A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures. 

I dagens byggprojekt används en mängd olika material för att bygga konstruktioner. Det förekommer att komponenter av aluminium gjuts in i betong vilket medför en risk att täckskiktet spricker p.g.a. korrosionsprodukternas stora volym. Därför är det viktigt att klargöra vilka korrosionsegenskaper aluminium har ingjuten i betong.

Generellt sett så har rostfria stål en hög korrosionsresistens i atmosfärisk miljö p.g.a. den mycket tunna oxidfilmen på ytan, en film som fungerar som en barriär och försvårar initieringen av en korrosionsprocess på stålets yta. Dock så kan rostfria stål få svåra gropfrätningsangrepp i vissa aggressiva atmosfärer där t.ex. klorider och SO2 finns närvarande. Olika ytstrukturer kan ge ytan olika egenskaper som vätbarhet, ytråhet och ytsammansättning. En yta som har hög vätbarhet har en tjockare fuktfilm på ytan jämfört med en yta som har låg vätbarhet. Det är i fuktfilmen på ytan som korrosionsprocesserna sker, aggressiva partiklar och gaser kan tas upp i fuktfilmen från atmosfären och öka korrosionshastigheten. Ytråheten påverkar både vätbarhet och hur mycket partiklar som fastnar på en yta, därmed påverkar ytråheten korrosionshastigheten. Ytsammansättning anger vilka och hur mycket det finns av ett ämne i den skyddande oxidfilmen, ämnen som kan ha betydelse för hur lätt korrosion uppstår, t.ex. så kan olika sulfider fungera som initieringsyta för korrosionsangrepp. I litteraturen har det dragits olika slutsatser om vilken ytegenskap som har störst betydelse för korrosionens omfattning. Vissa studier säger att ytråheten har störst betydelse medan andra säger att ytsammansättningen har störst betydelse. Särskilt låglegerade ferritiska rostfria stål kan få svår gropfrätning i aggressiva miljöer och då har typen av ytstruktur liten betydelse för hur stora korrosionsangreppen blir. För de mer legerade austenitiska stålen kan typen av ytstruktur ha stor betydelse för storleken på korrosionsangrepp. Höglegerade stål som innehåller molybden har generellt sett små korrosionsangrepp och typen av ytstruktur har liten betydelse för korrosionsangreppens omfattning. Sammantaget tycks det dock vara så att ytråheten ändå har relativt stor inverkan på korrosionsresistensen, dock har relativt få studier genomförts där ytråheten verkligen mätts.

För betongkonstruktioner som är exponerade i aggressiva miljöer kan korrosionsskador uppstå som kräver kostsamma reparationer. Aggressiva miljöer kan t.ex. vara konstruktioner i kontakt med havsvatten där klorider kan transporteras genom betongskiktet fram till armeringen och där orsakar korrosionsskador. För att förhindra vissa korrosionsskador kan armering av kolstål (som är det vanligaste armeringsmaterialet) bytas ut mot armering i rostfritt stål. Idag finns en mängd olika rostfria stål, med olika korrosionsegenskaper, tillgängliga på marknaden och det är därför viktigt att kunna klassificera korrosionshärdigheten för dessa stål. I en tidigare litteraturstudie ”Elektrokemiska metoder för utvärdering av armeringskorrosion samt kritisk kloridjonkoncentration för rostfritt stål i betong” [1] så undersöktes vad som har rapporterats i litteraturen om provningsmetoder för att undersöka korrosionshärdigheten för rostfritt stål i betong. Det framgick av litteraturstudien att en potentiostatisk metod med polarisering till +200 mV kan vara lämplig. I denna studie har en liknande potentiostatisk metod tillämpats och utvärderats. Provkropparna placerades i ett vattenbad där temperaturen ökade med 5°C per 14 dagar från lägst 20°C till maximalt 40°C. Två austenitiska och tre duplexa stål har undersökts och resultaten visar att stålen EN 1.4301 (304), EN 1.4162 (2101), EN 1.4436 (316) fick korrosionsangrepp vid 4 vikt-% Cl per cementvikt när temperaturen på vattenbadet var mellan 20 och 30°C. Det mer legerade duplexa stålet EN 1.4362 (2304) fick korrosionsangrepp vid 6 vikt-% Cl per cementvikt vid en temperatur på 35°C. Det högst legerade stålet EN 1.4462 (2205) fick inga korrosionsangrepp vid10 vikt-% Cl per cementvikt som var den högsta kloridkoncentrationen.

Aluminum-based sacrificial anodes were installed to reinforced concrete to stop ongoing corrosion in cooling water tunnels in a Swedish nuclear power plant. The steel rebars were also unintentionally connected to stainless steel water pumps. Therefore, the consumption rate of the sacrificial anodes was higher than predicted. An experimental and a field study were performed to assess if the steel rebar suffer from galvanic corrosion and if the stainless steel pumps are responsible alone for the high consumption rate. It was found from the experimental study that there is an increased risk of galvanic corrosion for steel rebar when the corrosion potential is raised to -200mV (SCE) for samples with 1% CL- by mass of cement and -500mV (SCE) for samples with 2% Cl- by mass of cement. The experimental results were compared with the corrosion potential measured in the cooling water tunnel where sacri ficial anodes were in use and not mounted at all. The cooling water tunnel without sacrificial anodes had generally more anodic corrosion potentials compared to the tunnel with anodes. The tunnel with anodes had also more anodic potentials closer to the stainless steel pumps than further away which means that the rebar is affected by the stainless steel pumps. However, the measured corrosion potentials in the tunnels were not as anodic as the potentials needed for high galvanic current measured in the experimental study.

Reinforced mortar samples were exposed in humidity chambers with different relative humidity or exposed in cyclic moisture conditions. The rebars were in an “as received” condition meaning that the preexisting oxide scale were intact. The lowest chloride concentration that initiated corrosion was 1% Cl− by mass of cement, corrosion was then observed for samples exposed at 97% relative humidity. It is suggested that the corrosion rate decreases when samples are exposed to a relative humidity lower than 97%. The results indicate that threshold levels should be evaluated at rather humid conditions (97%) despite the fact that the maximum corrosion rate at higher chloride levels is observed in the interval 91–94%. For samples exposed to cyclic moisture conditions, a lower chloride concentration was needed to initiate corrosion compared to samples exposed in static moisture conditions.

The electrochemical properties of various iron oxide scales on steel exposed in saturated calcium hydroxide solutions were investigated. The iron oxide scales were manufactured by different heat treatments and grinding processes and characterized using X-ray diffraction and scanning electron microscope. The electrochemical properties of the scales were assessed by measuring the corrosion potential and using electrochemical impedance spectroscopy and potentiodynamic polarization curves. It was found that wustite and magnetite are less noble compared to hematite but are more effective as cathodic surfaces. The results show that the electrochemical properties of the mill scale can be an important contributing factor in the corrosion of steel in concrete.

The development of highly ordered and self-assembled magnetic nanostructures such as arrays of Fe or Ni nanowires and their alloys is arousing increasing interest due to the peculiar magnetic properties of such materials at the nanoscale. These nanostructures can be fabricated using nanoporous anodic alumina membranes or self-assembled nanotubular titanium dioxide as templates. The chemical characterization of the nanostructured layers is of great importance to assist the optimization of the filling procedure or to determine their manufacturing quality. Radiofrequency glow discharge (RF-GD) coupled to optical emission spectrometry (OES) is a powerful tool for the direct analysis of either conducting or insulating materials and to carry out depth profile analysis of thin layers by multi-matrix calibration procedures. Thus, the capability of RF-GD-OES is investigated here for the in-depth quantitative analysis of self-aligned titania nanotubes and self-ordered nanoporous alumina filled with arrays of metallic and magnetic nanowires obtained using the template-assisted filling method. The samples analysed in this work consisted of arrays of Ni nanowires with different lengths (from 1.2 up to 5 μm) and multilayer nanowires of alternating layers with different thicknesses (of 1-2 μm) of Ni and Au, or Au and FeNi alloy, deposited inside the alumina and titania membranes. Results, compared with other techniques such as scanning electron microscopy and energy-dispersive X-ray spectroscopy, show that the RF-GD-OES surface analysis technique proves to be adequate and promising for this challenging application. © 2009 Springer-Verlag.

The effect of digested sewage sludge as a fuel additive to reduce corrosion of furnace walls has been studied. The nickel base alloy Alloy 625 and the iron-chromium-aluminium alloy Kanthal APMT™ were exposed for 14.25. h at the furnace wall in a power boiler burning 100% used (also known as waste or recycled) wood. The test was then repeated with the addition of sewage sludge to the waste wood. The samples were chemically analysed and thermodynamically modelled and the corrosion mechanisms were investigated. The results showed that the co-firing of sewage sludge with recycled wood leads to a reduction in the corrosion. Attack by a potassium-lead combination appeared to be the main corrosion mechanism in Alloy 625 during waste wood combustion, while attack by alkali chloride was found to be dominant in APMT alloy.

In the automotive industry a commonly used material is thin steel sheets coated with a thin layer of zinc for corrosion resistance purposes. Welding of this material, with the high temperatures involved, causes problems with zinc burn-off leading to reduced corrosion resistance. The zinc evaporation also causes arc disturbances leading to spatter formation, pores and difficulties achieving good visual weld quality. The joints are in many cases visible or semi-visible (e.g. visible after opening a door) and “A-grade” quality is demanded, meaning no visible discontinuities are allowed. It also implies a smooth and generally appealing appearance of the joint. An alternative to welding is brazing, and laser brazing meets the requirements but the process is associated with high costs. In the national project “LEX-B”, funded by Vinnova, the possibilities of using arc brazing, in particular one MIG/MAG brazing and two TIG brazing processes, for some automotive applications are investigated. This master thesis is connected to the first part of the project and aims at compiling data for making a selection of the most promising process to investigate and optimise further. LEX-B is conducted in cooperation between Swerea KIMAB AB, Volvo Trucks, Scania CV and University West. The joint of interest is a lap joint between bottom and upper sheets of 1.2 mm and 0.8 mm respectively that represents a joint on the side of a truck cabin. The requirements are visual A-grade quality and tensile shear strength of 300 MPa. In the project the MIG/MAG process Cold Metal Transfer (CMT) was compared to the TIG processes forceTIG and Plasmatron. CMT was experimentally investigated while the results for the other two processes were obtained partly from a previous study and partly from Volvo Trucks where tests were performed simultaneously. A system for measuring data for the process was developed, test specimens were brazed and examined visually and mechanical destructive testing was performed to ensure the tensile shear strength. Parameter studies were done for further process optimisation.

Distortions of mild steel structures caused by laser welding were analyzed. One thousand-millimeter U-beam structures were welded as overlap joints with different process parameters and thickness configurations. Final vertical and transverse distortions after cooling were measured along the U-beam. Significant factors, which affect distortions, were identified. Heat input per unit length, weld length, and sheet thickness showed a significant effect on welding distortions. Furthermore, the welding distortions were modeled using FE simulations. A simplified and computationally efficient simulation method was used. It describes the effect of shrinkage of the weld zone during cooling. The simulations show reasonable computation times and good agreement with experiments.

In this article, geometrical distortions of steel structures due to laser beam welding were analyzed. Two 700-mm-long U-beam structures were welded in overlap configurations: a double U-beam structure and a U-beam/flat structure. The structures were in different material combinations from mild steel to ultrahigh-strength steel welded with different process parameters. Different measures of distortions of the U-beam structures were evaluated after cooling. Significant factors of the welding process and the geometry of the structures were identified. Furthermore, welding distortions were modeled using two predictive finite element simulation models. The previously known shrinkage method and a newly developed time-efficient simulation method were evaluated. The new model describes the effects of expansion and shrinkage of the weld zone during welding and material plasticity at elevated temperatures. The new simulation method has reasonable computation times for industrial applications and improved agreement with experiments compared to the often used so-called shrinkage method.

One way to reduce the CO2 emissions in automotives is to reduce the weight of the Body-In-White. One easy to achieve the weight reduction is to replace steel sheet materials with Al alloys, which is 3 times lighter. One issue is the joining process, especially with combinations between steel grades and AL alloys. Example of combination of mixed material combinations (Al-steel) might be found in the door structure. The reason is because of the AL alloys worthier crash performance so the automotive manufacturer might want to use crash impact beams made by high strength steels in a AL intensive door structure. The joining process between aluminum and steel are problematic due it's not possible to use traditional spot-welding technologies due to the materials total difference in microstructure characteristics as well thermal properties. To overcome this issue then mechanical as well adhesion joining are frequently used. This paper describes a development process and subsequently analysis of a self-pierce rivet (SPR) process between 3 sheet metal combinations. The multi-material combinations in this study were a combination of ultra high strength steels sheets (DP1000) and a Al-alloy (AA 6014). The analysis of the SPR process, in sense of mechanical strengths, has been done by peel-and shear tests. To reduce the amount of future physical tests a virtual FE-model has been developed for the process. This FE model of the process has been subsequently used to analyze the mechanical strength during plastic deformation. By using inverse analysis a correct contact algorithm has been evaluated that would predict the binding force between the rivet and sheet under a deformation process. With this new virtual model it will not only possible to analyze and develop the SPR process but also to achieve the final strength of the joint. © 2011 American Institute of Physics.

Measurements of the thermal conductivity of casting powders are needed to determine the magnitude of the vertical heat flux in the powder bed of a continuous casting mould. The thermal conductivities and thermal diffusivities of four mould powders have been determined using the transient plane source (TPS) and the transient hot wire (THW) methods. The values reported in this investigation are in good agreement with the results of earlier studies which used the THW method. However, the results were significantly different from λeff values obtained in thermal insulation tests. This was attributed to the large contribution to λeff from gaseous conduction which arises from the large temperature gradient across the sample. It was found that the thermal conductivity (λpowd) of the powders had a mean value of 0.125±0.025 W m-1 K-1 for the four powders studied; this value is in good agreement with two other studies; it increased as the temperature increased with a mean temperature coefficient of (dλ/dT59×10-5 W m-1 K-2 for the range 295-1100 K and increased as the bulk density increased (λ295=0.010+1.69×10-4ρbulk W m-1 K-1).

Measurements of the thermal conductivity (λ) and thermal diffusivity (α) have been carried out on samples of Na2O·SiO2 and four mould slags for temperatures between 295 and 1300 K. These measurements were carried out using the transient plane source (TPS) method (295-373 K) and the transient hot wire (THW) technique (295-1300 K) and the laser pulse (LP) or laser flash method in the case of Na2O·SiO2 Values of l295 were very similar (1.07±0.03 W m-1 K-1) and all samples exhibited a maximum at the critical temperature (Tcrit 51040±10 K) beyond which there was a sharp drop in λTHW with increasing temperature. Measurements were also carried out on semi-crystalline samples with increasing λ and fraction of crystalline phase. These samples also exhibited a sharp drop in the thermal conductivity for temperatures above Tcrit and λTcrit was found to be 1.6±0.05 W m-1 K-1. Thermal conductivity (λLP) values calculated from reported thermal diffusivity (αLP) values were in very good agreement with the measured λTHW values for temperatures between 295 K and Tcrit but λLP values did not decrease with increasing temperature above Tcrit (cf. λTHW). Consequently, it was found that λLP≈7λTHW for mould slags.

The new HIP cooling systems enable very fast cooling rates under isostatic pressure. This does not only enable shorter HIP cycles but also allows complete heat treatment cycles to be performed in one HIP cycle. It has been shown in previous studies that extreme pressures of several thousand bar can push phase transformation towards longer times. The new URQ HIP cooling systems give the opportunity to investigate the impact of pressures up to 2000 bar on phase transformation time dependency. For each of the two materials in this study, a comparison of austenite phase transformation time at 100 and 1700 bar was performed. The study was performed by isothermal heat treatment of specimens for a specific time followed by quenching. To evaluate the influence of pressure on hardenability, the phase fractions were evaluated using grid method on SEM images. The study found significant influence of HIP pressure on hardenability.

The original purpose of this research was to develop a method for fast, simultaneous analysis of both the steel and slag content of heterogeneous metallurgical samples for process control. The method is based on Laser Induced Breakdown Spectroscopy (LIBS). The reason for choosing LIBS is that it can be employed for both conductive and non-conductive materials, and is relatively insensitive to sample shape and surface finish. The heterogeneous samples produced contain large numbers of sub-millimetre slag particles that cannot be completely separated from the surrounding steel in a LIBS analysis. A method has therefore been developed to perform a line scan analysis with approximately 0.5 mm resolution and 10 mm length along the sample. The laser pulse rate is 20 Hz and the scan speed is 1 mm/s. Slag particles appear in the line scan as "polluted areas" of the steel with very high concentrations of e. g. Ca, Al and Si. A mathematical model was developed to evaluate the data in steps, based on a single calibration. Firstly, "clean steel" areas are identified and the steel composition determined. In the second step, the average composition across the entire length of the scan is determined. In the final step, the average slag composition is determined by means of a difference calculation. The method was tested on several samples from the development of the heterogeneous sampler. It was found that the elements C, Si, Mn, P, S and Al can be determined in the steel with an RSD of a few percent. In the slag, the RSD's are higher, around10% for several important elements. It is expected that the method can be further developed for rapid analysis of smaller non-metallic inclusions.

Virtual weldability testing and prototyping significantly reduces the time and cost needed in product and process development. However, implementation is often inhibited due to lack of accurate information, support tools and methods to capture all knowledge elements from across the development process. Furthermore, results from previously conducted tests are often unavailable due to absence of knowledge reusability schemes and enabling tools. In this paper, a knowledge platform development is presented which has been implemented in industrial cases from Swedish automotive industries. The platform is demonstrated to be a key element in enabling effective virtual testing and prototyping. © 2018 The Authors.

This research aimed to assemble and review data that are relevant to sheet metal formability of the magnesium alloy AZ31. Rolled sheets were processed to give four different grain sizes in the range from 2.9 to 47.1 μm. Similar basal textures were present in all these conditions. Tensile tests were carried out at various temperatures between 25 °C and 240 °C, with some additional tests also made below room temperature in dry ice. Results are presented and discussed relating to strength, ductility, strain rate sensitivity and anisotropy. An optimum grain size of about 7 μm applies for ductility over most of the temperature interval. Uniform elongation decreases steadily with increasing temperature whereas the post-necking and total elongation values increase markedly. Measurements of strength, anisotropy and strain rate sensitivity all indicate a significant role of grain boundary mediated deformation above room temperature. The plastic strain ratio, r, is high at room temperature but decreases considerably, especially for the fine grained conditions, at higher temperatures. Modifications to the active slip modes also occur over the same temperature interval but their effect on plasticity is probably less important than was previously believed. © 2012 Elsevier B.V.

Materials selection in the oil and gas industry relies on engineering standards, such as NACE TM0177 and NACE TM0284, which stipulate that oxygen contamination should be avoided during materials testing in H 2 S-containing media. In this second paper, as part of a series of articles that evaluates how traces of oxygen modify the corrosion of pure iron and hydrogen permeation across iron membranes in H 2 S-containing solutions, the impact of changing the H 2 S partial pressure from 100 kPa to 0.1 kPa was investigated. It was found that bulk solution chemistry for all H 2 S partial pressures changes with time, due to the formation of H 2 S–O 2 reaction products (sulfates, sulfites, and thiosulfates), which results in bulk solution acidification. Electrochemical and weight-loss measurements confirm that Fe corrosion rates in baseline well-deaerated H 2 S-containing solutions decrease with decreasing H 2 S partial pressure, although these are observed to be much higher under continuous oxygen contamination. With decreasing H 2 S partial pressure, hydrogen uptake in Fe also decreases, due to lower and lower concentrations of dissolved H 2 S and the associated increase in pH. However, even at 1 kPa and 0.1 kPa H 2 S, permeation effciencies remain close to 100% when no O 2 contamination is present. The hydrogen uptake is always relatively lower in Fe exposed to oxygen-polluted H 2 S solutions. Permeation efficiencies decrease continuously. From electrochemical data and surface characterization, these observations at lower H 2 S partial pressures are attributed to the disruptive effect of oxygen on the nature of sulfide corrosion products, and hydrogen entry promotion, along with the contribution of an additional cathodic reaction that does not result in hydrogen entry into the metal

Corrosion of iron exposed to H2S saturated solution at pH 4 was studied by electrochemical impedance spectroscopy, weight loss coupons and surface analysis. Hydrogen permeation was also used as indirect means of evaluating the intensity of the proton reduction reaction leading to hydrogen entry into the metal. Since corrosion in this type of test solution results in the rapid build-up of a conductive and highly porous iron sulfide scale, a specific contribution of the film has to be considered. An impedance model was thus proposed. The faradaic anodic impedance consists of a two-step reaction with charge transfer and adsorption – desorption. An additional contribution, associated with the conductive and highly porous iron sulfide film was added in parallel. This contribution, mostly visible in the low frequency domain, presents a 45° tail associated with a porous electrode behavior. This model was well adapted to describe impedance diagrams measured at various exposure times, up to 620 h. Charge transfer resistance determined from impedance analysis allowed calculating the evolution with time of the corrosion current density. A very good correlation was found between this corrosion current density and the hydrogen permeation current density. As expected in our experimental conditions, a permeation efficiency close to 100% is demonstrated. Corrosion rate of 490 μm/year was measured by weight-loss specimens, confirming the validity of the impedance analysis, which resulted in a calculated corrosion rate of 530 μm/year.

Materials selection in the oil and gas industry relies on engineering standards, such as NACE TM0177 and NACE TM0284, which stipulate that oxygen pollution should be avoided during materials testing in H2S-containing media. In this paper, we explore the manner in which traces of oxygen can modify the test solution chemistry and the corrosion of/hydrogen permeation across iron membranes in H2S-containing solutions. Oxygen pollution is shown to strongly influence solution chemistry, through the introduction of sulfur-oxygen reaction products resulting in bulk acidification. Weight loss, electrochemical methods, and solution chemistry measurements conclude that iron corrosion rates in the presence of oxygen pollution are doubled, when compared against the control system (without oxygen pollution). Unexpectedly, despite a lower pH and higher corrosion rates in the oxygen-polluted H2S-containing solutions, the hydrogen permeation rate decreases monotonically, relative to the control. We discuss how this observation is most likely related to a disruption of sulfur adsorbates involved in hydrogen entry promotion. 

The plastic anisotropy of magnesium alloy sheet drops rapidly with test temperature. It has previously been suggested that this may be due to an increase in the activity of 〈c+a〉 dislocations. The present note points out that the phenomenon may result, instead, from the action of grain boundary sliding. This can explain the strong effect of grain size on anisotropy. Furthermore, it points to a new avenue for alloy development. © 2009 Acta Materialia Inc.

The paper describes in principle how information about textures can be obtained through the application of laser-ultrasonics (LUS) which can be carried out at elevated temperatures, for example in connection with hot rolling. The benefits from getting a measure of texture in this way are explained together with the proposed methodology which is based on the elastic anisotropic properties of the textured material. Measurements are made using only a single laser pulse and in real-time. Two approaches are presented to modelling the propagation of elastic waves, ray tracing and finite difference modelling. These give consistent results but the latter provides a more complete prediction of the ultrasonic spectrum that can be quantitatively related to measured signals through a cross-correlation procedure. Some experimental results are presented for room temperature measurements on a sheet of interstitial-free steel. Agreement between experimental data and modelling results is good and allows estimation of the 4th order coefficients of the orientation distribution function.

This review is focused on a comparison of LIBS with the two most common plasma Optical Emission Spectroscopy (OES) techniques for analysis of metals; spark OES and glow discharge (GD) OES. It is shown that these two techniques have only minor differences in analytical performance. An important part of the paper reviews a direct comparison of the analytical figures of merit for bulk analysis of steels using spark and LIBS sources. The comparison was carried out using one instrument with interchangeable sources, eliminating differences related to the optical system and detectors. It was found that the spark provides slightly better analytical figures of merit. The spark analysis is considerably faster, the simple design of the spark stand has enabled complete automation, both properties of great importance in the metallurgical industry for routine analysis. The analysis of non-metallic inclusions (NMI) with spark and LIBS is presented, in the case of the spark this has become known as Pulse Distribution Analysis (PDA). A very significant difference between the techniques is that the electrical spark typically evaporates ~ 100 times more material than a single laser pulse, resulting in complete evaporation of an NMI present in the evaporated metal. The major advantage of LIBS is that it is localised with very good lateral resolution. The major advantages of spark is that it is much faster (can be done simultaneous with the bulk analysis) and easier to quantify. Compositional Depth Profiling (CDP) is compared for GD-OES and LIBS. It is shown that for applications where GD-OES is well suited, e.g. coated metallic sheet, GD-OES still performs slightly better than LIBS. Similar to the case of NMI analysis, the major advantage of LIBS is the great lateral resolution. This allows elemental surface mapping, as well as CDP of very small areas on μm scale. One further advantage of LIBS is that samples of almost any material, shape and size can be analysed, whereas GD-OES has only limited capabilities for non-flat and small samples. A general conclusion of this review is that LIBS is not likely to replace spark and GD-OES in the foreseeable future, for applications where these techniques are well suited. On the other hand several new applications, particularly in the field of on-line monitoring of industrial processes, are making great inroads for LIBS in the metallurgical and manufacturing industries.

The purpose of the work is to develop a general method, to predict the corrosion resistance of Zn-based coatings, expressed as total mass loss in an accelerated salt spray test. The method is to be based on just three analytical parameters; the total coating weights of Zn, Al and Mg. The reason for this restriction is that determination of these three parameters is possible in on-line analysis. The predicted corrosion resistance could then be included in a process/quality control system. Accelerated corrosion tests have been carried out by Swerea KIMAB IC (Institut de Corrosion) in Brest, and CRM in Belgium. Test were run according to the Renault ECC1 test D172028/-C (12 weeks), and with an accelerated cyclic corrosion test developed by CRM. The materials were divided into four corrosion classes according to total mass loss. All corrosion experiments show clearly the well documented positive influence of magnesium and aluminium. In relation to the masses of these elements in the coatings, the influence of both elements is considerably higher than the influence of zinc alone. For this reason, a new quantity is introduced, called "equivalent Zn coating weight". This quantity is a linear combination of the coating weights of zinc, aluminium and magnesium. A model for prediction of corrosion resistance was developed with the expert system, based on a combination of regression analysis and a "decision tree" algorithm. The model was able to correctly classify 25 out of 27 materials based on just the three analytical parameters mentioned above: the total coating weights of zinc, aluminium and magnesium. In conclusion, the approach shows that an accurate prediction of the corrosion behaviour is possible even on-line. For purposes of material development, the expert system can also be expanded to include additional analytical parameters.

Glow Discharge Optical Emission Spectroscopy (GD-OES) is a well established technique for Compositional Depth Profiling (CDP), very useful for in-depth elemental analysis of surface layers from 10 nm to 100 µm. It is fast, sensitive and fully quantitative. However, there are a few artefacts requiring further study to improve the accuracy and trueness of the method further, primarily for near-surface applications. Outgassing of volatile compounds present inside the source, mainly water and hydrocarbons, has been established to be a major cause of such artefacts. The most “problematic” element is hydrogen, for the following two reasons: 1) it “cools” the plasma even when present in small quantity and thereby affects the intensities of the emission from almost all other elements; 2) it is very reactive and forms molecular species with other light elements e.g. CH, NH and OH, having emission spectra overlapping several atomic analytical lines; causing “false” or exaggerated surface peaks of the corresponding elements. In this work, methods to reduce the outgassing of volatile compounds have been studied. Attempts to dry and clean the argon gas flowing into the source by means of a chemical filter gave no significant improvement. On the other hand, replacing the “standard” anode made of a copper-beryllium alloy with a pure copper anode was shown to reduce the outgassing significantly. To be more specific, the background signal from atomic hydrogen and associated artefacts are reduced, it is still possible that the amount of molecular hydrogen remains almost constant, without observable effects on the analytical signals. Since molecular emission can originate from the sputtered material of the sample itself, particularly organic coatings, an in-depth study of molecular emission in GD-OES was carried out. It was shown that background signals from such emission can be significantly reduced, provided that the instrument has spectral channels for the emitting molecular species installed. With such channels available, conventional “line interference correction” methods was found to be effective in reducing false elemental signals from molecular emission. Application of the pure copper anode and reduction of molecular background techniques to a heat treated zinc-base coating showed expected improvements in the near-surface part of the depth profile. However, for the major elements of technical importance, the difference compared with the original anode and analytical method was marginal. This is reassuring, since it means that the near-surface artefacts normally do not cause major analytical errors. The element that is most difficult to establish the “trueness” of depth profiles is nitrogen, especially if the surface layer is slightly porous. There are samples where an elevated signal from nitrogen in the top surface cannot be correlated to a vacuum leak, trapped air or molecular emission (CO). Investigations where samples are measured for total nitrogen with conventional techniques are very difficult, since the surface layers showing an elevated content are very thin. Further investigation of such samples with high vacuum techniques, e.g. SIMS, would be of interest. A second part of the project deals with advanced evaluation of depth profile data by means of “expert systems”. An expert system is a computer application that is able to perform tasks which are normally performed by human experts; in this case the aim is to be able to perform e.g. quality control with GD-OES without the need for a qualified human expert to interpret the data. There are several types of “computational statistics” methods that can be employed for such purposes, the most well known is probably multivariate analysis. Other methods can evaluate both numerical and other types of input related to classification based on technical properties, e.g. paint adhesion, scratch resistance etc. The objective of this work is to be able to classify samples according to such technical properties. All such systems need a “training set” of samples with known technical properties. In this work, a relatively large set of steel sheet samples with various zinc-based coatings were classified according to corrosion resistance. Form the GD-OES depth profiles, the coating weights of zinc, aluminium and magnesium were extracted in a data pre-treatment step. Using the rule-based classification algorithm “decision tree” 25 out 29 samples was correctly classified. This “proof of concept” work has shown that it is possible to predict certain technical properties based on a multi-element depth profile. This opens up the possibility for e.g. automated quality inspection of complex coating systems, but also the possibility to use GD-OES depth profiling more effectively as a tool in product development.

The aim of this project was to investigate the potential of applying computational statistics (“data mining”) methods to PDA – OES data to find correlation to defects in the final products as well as changes of parameters during the steelmaking process. The computational methods used were multivariate (MVA) data analysis and the rule-based methods “decision trees” and “neural nets”. The project was carried out in close cooperation with Outokumpu Stainless Avesta and the Royal Institute of Technology (KTH). PDA – OES data from sheet samples with and without surface defects were processed by all three methods, all showing statistically significant and consistent correlation. The formation of surface defects is positively correlated to the number of “medium” to “large” inclusions of the classes AlCaMg and AlCa i.e. mixed oxides of these elements. The second part of the research was an evaluation of variations in inclusion characteristics in different process stages using synthetic slags. A large number of samples were collected from experimental trials with two types of synthetic slags, and the conventional process without slag addition for reference. The samples were taken in the ladle furnace at three stages, and in the tundish in connection with the final test sample before casting. PDA – OES data from these samples were evaluated with MVA and decision tree methods. The results showed that the different process stages can be identified from the PDA-OES data with rather good certainty. No significant difference between the use of synthetic slags and the conventional process was detected. In the course of the evaluation work, it was also found that the computational statistics methods must be used with caution. The reason is that data due to “statistical noise” can be identified as significant, giving misleading results. Further work to reduce this problem will be necessary.

The technique PDA/OES is briefly reviewed. It is based on detection of the signals from individual sparks in OES analysis, which usually comprises a few thousand sparks in each burn. Sparks hitting inclusions/particles of characteristic elemental composition give rise to “outliers” of higher intensity for “marker” elements characteristic of the particle type. The outliers are extracted by statistical analysis, and processed by the software to identify and quantify the particles. PDA/OES is used mainly in the steel industry, where the main interest is to detect and analyse non-metallic inclusions (NMI). In this work, PDA/OES has been tested for applicability to aluminium alloys. In this case the main interest is metallic particles, but there are also some types of NMI’s of interest. It was found that PDA functions in the same way as in steels, but there are several factors limiting the applicability. Firstly, the smallest detectable particles are about 1 μm diameter, and the particle number density should not exceed about 20000/mm3 for PDA to detect then as individual particles. In aluminium, many particles (precipitates) of interest are much smaller and present in much higher number densities. Secondly, the elements present in the metallic particles also exist as dissolved in the surrounding metal, giving a high and noisy background which limits the possibility to detect signals from the particles as outliers. These constraints has limited the applicability to metallic particles in the several μm range, using Fe as the “marker” element. However, for certain types of NMI it is likely that very small particles down to 1 μm can be detected. The experimental work has shown that the scanning spark technique OPA can provide additional useful analytical information. Macroscopic segregation at the mm – several cm ranges can rapidly be investigated in two dimensions. In combination with PDA, macroscopic “clusters” of particles can be mapped.The spark optical emission techniques PDA/OES and Original Position Analysis (OPA) have been investigated for application to aluminium alloys. PDA/OES has been optimised for detection and quantification of metallic particles in the several µm range with. The OPA technique has been evaluated for rapid determination of macroscopic segregation.

The purpose of the work is to further develop and validate the optical emission method pulse distribution analysis (PDA) for rapid inclusion characterisation in steel production. The experimental work was focused on investigation of several operational parameters: spark energy, spark frequency and time gating of signal acquisition. The results showed that a low spark energy improves the detection limit, but at the expense of measuring statistics due to a smaller sample volume. The measuring frequency proved to have no significant influence on the analytical results, but several existing instruments cannot handle the highest spark frequencies above about 300 Hz in PDA mode due to limitations in the electronics. Investigation of time gating (TRS) gave only a marginal improvement in the detection limit of Si outliers above the metallic content. The work also revealed that there is a risk to detect "false" outliers due to asymmetric intensity distributions. This has resulted in the development of more advanced algorithms for outlier detection, increasing the accuracy of the method. Another limitation found is that the particle number density must not exceed about 10 000 inclusions/mm3 for the method to effectively detect single inclusions. A method to overcome this limitation has been suggested, but not yet evaluated. The accuracy of quantitative determination of the Al content in inclusions has been verified by reference methods. In conclusion, it has been demonstrated that state-of-the-art PDA is a very powerful technique for rapid inclusion characterisation in steels. Furthermore, the speed of analysis is sufficiently high for process feedback and controllable.

The objective of this project is to evaluate commercially available techniques for trace elemental analysis of steels using direct solid sampling. Such methods have the potential to increase sample throughput and thereby reduce analysis costs. Glow Discharge Mass Spectrometry (GD-MS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) were evaluated. Five certified reference materials (CRM) were selected for the experimental work; a high purity iron, a carbon steel and three high alloy steels. For both types of instruments, the sample set was first used for calibration, then run as unknowns several times in order to get sufficient statistics for the evaluation. The GD-MS measurements were carried out at the Thermo Fisher Scientific applications laboratory in Bremen. The LA-ICPMS work was carried out at KIMAB. Prior to the measurements reported here, the effects of varying instrumental parameters of LA-ICPMS were investigated in order to develop a suitable method for steels. The results show that both techniques are powerful methods for simultaneous determination of a large number of trace elements in steels. A limitation is that none of the techniques is capable of analysing C, N and O, due to gas leaks and contamination from materials in the sources. The overall performance in terms of precision and detection limits is better for GD-MS, but for several applications LA-ICPMS provides sufficient performance. Both techniques have instrumentally limited detection limits at the ppb level or below, but the results on the test samples mostly give considerably higher standard deviations, also at very low concentration levels. Therefore, the analytical accuracy for traces is more limited than one would expect based on the instrumental capabilities; typically in the low ppm range or slightly below. The most likely reason for this is the combination of material inhomogeneity and small sampling volumes. This affects LA-ICPMS the most, due to considerably lower sampling volume than GD-MS.

Accurate determination of trace elements in steels is of importance for several reasons. Some trace elements are added on purpose to influence the metallurgy of the steel, and it is important to control the content to the correct level. Other trace elements are deleterious to certain steel properties and must be controlled to be below maximum levels in order to ensure the quality. In more recent years, national and international legislation demand from steel producers to declare the content of certain environmentally hazardous elements, mainly heavy metals such as Hg, Pb and Cd. Multi-element techniques based on direct solid sampling is of great interest due to the short analysis times, but there is a lack of suitable reference materials (RM) for calibration. Bundesanstalt für Materialprüfung (BAM) in Berlin has therefore developed a technique to produce synthetic solid RM’s for trace analysis. The technique is based on mixing metal powder with small amounts of trace elements in liquid solution, drying and compacting the powder into solid briquettes. A few stainless steel RM’s produced at BAM were used at KIMAB to determine Ce, La, Nd and Pr in a stainless steel CRM, using an LA-ICPMS instrument. The results showed very good agreement with certified values. Six RM’s of the same type were subsequently prepared at KIMAB, doped with Pb, Cd and Hg at levels from 0,1 μg/g to 30 μg/g. The RM’s were first analysed by wet chemical ICP-MS at ALS in Luleå. The results showed nearly 100% recoveries of Pb and Cd, while most of the Hg had been lost in the sample preparation. The samples were then used to calibrate the LA-ICPMS instrument for Pb and Cd. It was found that the signals from the top surface of the samples were very high, indicating a considerable degree of “elemental fractionation. A “preburn” in the form of an ablation linear scan across the sample surface was therefore needed prior to the analysis scan. Very good linear calibration curves were obtained for Pb and Cd, but with apparently higher background levels than in solid steel. Three stainless steels with previously determined contents of Pb just below 2 μg/g were analysed together with the synthetic RM’s, giving intensities significantly below the calibration curve. Assuming a zero background level give calculated mass fractions in near agreement with certified values, but this is not a satisfactory calibration method. It is therefore concluded that in present form, synthetic RM’s are only reliable as calibration samples for LA-ICPMS measurements at trace levels larger than 10 μg/g. Further work is necessary in order to reduce this limit

In the present context of oil price down turn and enhanced competitiveness, cost saving becomes more important than ever. As part of cost reduction solutions in offshore projects, it may be envisaged to leave field joints bare on subsea pipelines instead of applying a field anticorrosion coating after welding of the joints on board the laying vessels. This approach would need to be applied to specific cases, where it would lead to reduction of cycle time and consequently laying rate improvement during offshore installation campaigns when field joint coating activities are on the critical path, like with pipeline J-laying method. Although cathodic protection is an efficient, reliable and field proven method for seawater corrosion prevention on steel exposed areas of subsea coated pipelines, a quantitative assessment of the long term behavior of the pipeline coating at the transition zone with the bare field joint is recommended in order to support such a radical change in the pipeline external corrosion protection philosophy. Therefore, a bespoke experimental setup was designed to simulate bare field joint configuration under cathodic protection over a long term exposure in seawater together with long term cathodic disbondment tests for comparative purpose. The bespoke experimental test was performed at full scale on 3LPE coated pipe section with a field joint area left bare and protected by galvanic anodes. The pipe was immersed in a vessel containing renewed seawater and half-buried in mud to reproduce actual pipelines exposure on seabed. It was heated also with an internal fluid at 65°C to simulate actual operating conditions. Long term cathodic disbondment tests were performed on 3LPE coated pipe samples with internal heating of the samples at 23°C and at 65°C. Reference samples without CP were also exposed to the same conditions. The two experimental works were conducted during 12 months. For each of the tests above, a visual assessment was performed at regular intervals together with a quantitative assessment of the disbonded area (removal and recording of disbonded coating area). With these tests, it was possible to characterize the influence, over the time (up to one year) of the temperature over the normalized cathodic disbondment test results. The effect of the cathodic protection was also evaluated. For the full scale test evaluation and characterization, comparison was made between the disbonded coating length in the mud and the seawater exposure conditions. Correlation between cathodic disbondment tests and full scale test was also drawn. In light of the results obtained so far in this study, these tests results conclude positively that the bare field joint alternative concept for subsea pipelines is possible upon certain operating temperature limitation.

Digital Image Correlation (DIC), Acoustic Emission and Electrochemical Noise measurements were applied to study the growth of multiple intergranular cracks as a colony on an Alloy 600 in a tetrathionate solution. Cracks exceeding 55 μm in length and 0.45 μm in opening were successfully detected by DIC. Moreover, crack population was classified into initiating, active and dormant cracks, active population being the larger one. The emergence and intensification of interactions produced a modification on the colony growth behavior. They range from a mostly surface crack propagation (in the absence of interactions), to in depth propagation predominantly governed by crack shielding

A new thermodynamic database has been combined with an existing kinetic database to perform coarsening simulations in ternary systems including MC and M7C3 carbides in an fee matrix. The kinetic database was revised taking into consideration the new experimental information on the Fe-Cr-V-C system obtained in the present work, and available experiments on the ternary Fe-Cr-C and Fe-V-C systems. After revision the agreement between experimental results and simulations was satisfactory. It was found that the interfacial energy of M7C3 was twice as large as that of the MC carbide. The calculations for commercial steels with 6 alloy elements gave results in satisfactory agreement with new experimental measurements. The present coarsening simulations use the calculated equilibrium state and the observed particle sizes as the state for the start of the simulations. All the simulations were performed with the DICTRA software. © 2008 Institute of Materials, Minerals and Mining.

Three sinter steel materials, AD15, AD4 and Astaloy CrM, have been under evaluation in this study. The study has been focusing on three types of trials in order to see how the sintering parameters influence the reduction of oxides. The first series of trails were focused on how the green body density affects the reduction rate. The second and third series of trail were more focused on the sintering parameters, i.e. sintering time and sintering atmospheres, respectively. For sinter steel pellets a clear effect of the green body density can be seen on PAS and oxygen analyses. A higher green body density decreases the oxygen reduction reactions during sintering and results in higher oxygen content in the final pellet. How the hydrogen content in the sintering atmosphere affects the reduction efficiency is still not clear as the results from the PAS and the chemical and microstructure analysis had different outcome. Further studies are required. The total reduction time has effect on the reduction result i.e. a longer reduction time will reduce more than a faster reduction time.

In this work, correlation between the oxide formation and pickling behaviour of a conventional duplex material - 1.4462 is reported. The materials investigated are the duplex grade 1.4462 and two single phase alloys with compositions corresponding to the respective phases of the duplex material. Annealing was conducted at 1070 °C for 8 minutes. Topography and composition of the oxide layer were analysed with GDOES, FIB, XRD, SEM-EDS and CLSM. The ferritic steel formed a thick chromium-enriched oxide with a silica-rich sublayer. On the austenitic steel, ironenriched nodules were observed in the centre of the grains, together with oxide ridges on the top of the grain boundaries. The oxide on the duplex grade differed depending on the phase; nodule formation was observed on the austenitic grains while a more homogenous oxide formed on the ferritic grains. Pickling was performed in a mixed nitric/hydrofluoric acid bath. The fastest removal was observed for the austenitic sample, followed by the duplex and the ferritic samples. The oxide on the austenitic sample spalled from the surface while the oxide on the ferritic grade was removed by dissolution rather than by spallation. A mixed behaviour was observed on the duplex grade where some zones pickled faster than others.

The use of titanium plate heat exchangers is widespread for Offshore and Coastal installations where seawater cooling is required. Several years ago difficulties to supply titanium Grade 1 for this application triggered the need for qualification of other alloys for this application. Applications using passive alloys are especially susceptible to crevice corrosion when exposed to hot seawater. Since titanium is the most corrosion resistant alloy in seawater only highly corrosion resistant alloys could be considered for its replacement in plate heat exchangers. In addition since they need to be shaped into plates by cold pressing only alloys with a high formability could be selected. This narrowed even further candidate alloys for plate heat exchangers. In this study nickel chromium molybdenum alloys and a highly alloyed stainless steel were tested between 30 and 70°C in natural seawater with up to 1 ppm free chlorine. Rather than using short term electrochemical testing that is often difficult to compare with service performance long term exposure tests (up to 18 months) of real plate heat exchangers were carried out. These tests are considered to be more representative of actual service conditions. The results of these tests and their significance are discussed and compared with previous reported work.

The role of Sn on the atmospheric corrosion performance of binary Cu-Sn bronze alloys (4–6 wt.% Sn) compared with Cu metal used in outdoor architecture is elucidated in terms of microstructure, native surface oxide composition, patina evolution, corrosion rates, appearance and metal release. Results are presented for non-exposed surfaces and surfaces exposed at different urban and marine sites in Europe up to 5 years and based on multi-analytical findings from microscopic, spectroscopic, electrochemical and chemical investigations. Alloying influenced the corrosion, aesthetic appearance and patina evolution, differently for urban and marine sites, whereas no effects were observed on the release pattern. © 2019 The Authors

The control of the surface chemistry during sintering is the key factor for the successful and efficient production of PM parts, especially for powders containing elements with high affinity to oxygen such as chromium. The effect of different reducing agents was investigated by performing sintering trials on water atomized steel powder pre-alloyed with 3 wt.% Cr with and without the addition of graphite as well as using atmospheres with varying hydrogen content. The use of thermal analysis and photoacoustic spectroscopy in combination with results from fractographic investigation showed that oxide reduction is enhanced with the presence of hydrogen even if the main reduction mechanism is the carbothermal reactions. Oxides rich in Cr, Mn and Si were formed during sintering for all applied conditions. The findings are summarized in a simple model describing the enclosure of oxides during the sinter-neck development and the changes in surface chemistry during the process.

The use of elements with high oxygen affinity such as Cr or Mn in PM steels has been met with skepticism although such grades are attractive options for structural applications. They require strict control of the used atmosphere during the sintering process. Various techniques such as photoacoustic spectroscopy (PAS) and continuous CO/CO2/H2O measurements have been implemented for atmosphere monitoring during sintering trials of Cr-alloyed steel powder. The used atmospheres were nitrogen-hydrogen blends (0, 3, 10 and 100% H2) as well as vacuum. The progress of the oxidation/reduction processes was also followed with thermogravimetric studies. The pressed and sintered samples were examined using optical and electron microscopy in combination with EDX in order to evaluate the formed reaction products. The presence of hydrogen, even in small amounts, is positive for the oxide reduction. Results show that careful adjustment of the used atmosphere leads to efficient production of steel components based on Cr-prealloyed powders.

Metallic components manufactured via the Powder Metallurgy route require more attention in terms of adjusting the process parameters in order to control the chemistry during production. Therefore the first step towards a robust production through the Powder Metallurgy route is the characterization of the chemical features of the metal powder both on the surface and in the bulk This review is an assortment of examples of characterization studies used for investigating different features observed in metallic powders. ©Carl Hanser Verlag, München.

Steel produced by the PM-HIP route has a more homogenous microstructure compared with that obtained in conventionally produced material. This is an important advantage in many applications, and is therefore of interest to predict. The homogeneity of the microstructure is possible due to the rapid solidification of the powder grains in the atomization and the small size of the powder grains. Computational predictions of the variations of composition in powder grains, compacted material and conventionally produced material are compared with microstructure investigations. The microstructure is investigated in SEM with coupled composition analysis by EDS/WDS. The computational predictions are based on a description of the equilibria in the steel, and of the kinetics of segregation on solidification. The effect of alloying elements is discussed, and the effect in a stainless steel and in a tool steel is calculated.

In an effort to find alternative routes for the production of sintered parts, induction sintering has been considered a promising candidate because it incorporates short production times. This study is a novel approach which explores the possibility of producing PM steel parts by means of induction sintering. In this work, green compacts from Distaloy-DH powder have been induction sintered at different temperatures and by varying the sintering time and atmosphere. The role and behavior of lubricant and graphite additions during the process were also examined. Conventional sintering was also performed for comparison. Results from the microstructural investigation show complete dissolution of both the diffusion-bonded Cu and the admixed graphite during sintering. Induction sintered samples showed improved mechanical properties which were confirmed by fractographic investigation. The study shows that by careful adjustment of the different sintering parameters it is possible to acquire high performance PM parts through the induction sintering route.

This paper contributes to a TEM examination on the oxide films formed at three locations along a crack path in Alloy 182 weld from a BWR core shroud support leg, namely, the crack mouth, the midway between the mouth and the crack tip, and the crack tip. In the crack mouth the oxide film was approximately 1.6 μm in thickness and consisted of relatively pure NiO. The midway oxide film was mainly a nickel chromium oxide with a film thickness of 0.3 μm. At the crack tip the oxide film was a nickel chromium iron oxide with a film thickness of 30 nm. In all studied locations the main oxides had the similar rocksalt structure and the cracks were much wider than the thicknesses of the oxide films. It probably suggests that the corroded metal was largely dissolved into the coolant. The different dissolution rates of nickel, chromium and iron cations in the oxide films are clearly displayed with the compositions of the residual oxides. The oxide stability under different redox potentials along the crack path is briefly discussed.

This paper contributes to a TEM examination on the oxide films formed at three locations along a crack path in Alloy 182 weld from a BWR core shroud support leg, namely, the crack mouth, the midway between the mouth and the crack tip, and the crack tip. In the crack mouth the oxide film was approximately 1.6 μm in thickness and consisted of relatively pure NiO. The midway oxide film was mainly a nickel chromium oxide with a film thickness of 0.3 μm. At the crack tip the oxide film was a nickel chromium iron oxide with a film thickness of 30 nm. In all studied locations the main oxides had the similar rocksalt structure and the cracks were much wider than the thicknesses of the oxide films. It probably suggests that the corroded metal was largely dissolved into the coolant. The different dissolution rates of nickel, chromium and iron cations in the oxide films are clearly displayed with the compositions of the residual oxides. The oxide stability under different redox potentials along the crack path is briefly discussed.

Experimental verification of boron species in fuel CRUD (Chalk River Unidentified Deposit) would provide essential and important information about the root cause of CRUD-induced power shifts (CIPS). To date, only bonaccordite and elemental boron were reported to exist in fuel CRUD in CIPS-troubled pressurized water reactor (PWR) cores and lithium tetraborate to exist in simulated PWR fuel CRUD from some autoclave tests. We have reevaluated previous analysis of similar threadlike crystals along with examining some similar threadlike crystals from CRUD samples collected from a PWR cycle that had no indications of CIPS. These threadlike crystals have a typical [Ni]/[Fe] atomic ratio of ∼2 and similar crystal morphology as the one (bonaccordite) reported previously. In addition to electron diffraction study, we have applied electron energy loss spectroscopy to determine boron content in such a crystal and found a good agreement with that of bonaccordite. Surprisingly, such crystals seem to appear also on corroded surfaces of Alloy 600 that was exposed to simulated PWR primary water with a dissolved hydrogen level of 5 mL H2/kg H2O, but absent when exposed under 75 mL H2/kg H2O condition. It remains to be verified as to what extent and in which chemical environment this phase would be formed in PWR primary systems.

For more than 10 years now the National and Kapodistrian University of Athens, Greece, has contributed to the UNECE (United Nations Economic Commission for Europe) ICP Materials (International Co-operative Programme on Effects on Materials including Historic and Cultural Monuments) programme for monitoring the corrosion/soiling levels of different kinds of materials due to environmental air-quality parameters. In this paper we present the results obtained from the analysis of observational data that were collected in Athens during the period 2003-2012. According to these results, the corrosion/soiling of the particular exposed materials tends to decrease over the years, except for the case of copper. Based on this long experimental database that is applicable to the multi-pollutant situation in the Athens basin, we present dose-response functions (DRFs) considering that "dose" stands for the air pollutant concentration, "response" for the material mass loss (normally per annum) and "function", the relationship derived by the best statistical fit to the data.