Search

Austenitic stainless steel 1.4435, a candidate material for high-pressure tubing for hydrogen applications, was investigated in two different stages of cold deformation (0 and 27 %) regarding its hydrogen embrittlement tendency. The determination of effective diffusion coefficients revealed slightly increased diffusion kinetics at 60°C for the cold-reduced material (8.0 · 10−15 m²/s) compared to the solution annealed one (5.0 · 10−15 m²/s). High-pressure gaseous hydrogen charging shows no differences regarding the degree of cold deformation with a maximum hydrogen concentration of 112 wt.-ppm. Furthermore, a significant ductility loss expressed by the ratio of the reduction of area was observed. • Cold drawn material shows enhanced diffusion kinetics than solution annealed state. • Hydrogen contents of up to 112 wt.-ppm are present after gaseous charging. • No failure occurred in constant load tests at 90 % of the yield strength. • SSRTs show no significant decrease in fracture elongation due to hydrogen charging. • 1.4435 is applicable for hydrogen tank systems within the tested conditions. [ABSTRACT FROM AUTHOR]

Effect of shot-peening on the oxidation behaviour of alloy 304HCu in controlled advanced ultra-supercritical (AUSC) steam at 650 ◦C, 31 MPa for 600 h was investigated. Non-shot peened surfaces form thick Fe-rich oxides, undergo internal oxidation, and suffer oxide spallation sooner than those reported in literature. Shot-peened surfaces form a thin, external chromia scale with Mn(Cr,Fe) 2 O 4 and MnCr 2 O 4 spinels growing above and below it respectively. Shot-peening enhances Cr and Mn diffusivity through grain refinement and increased dislocation density, which aids in resisting chromia scale breakdown, eliminating iron oxides, and preventing oxide spallation. Oxide growth mechanism in AUSC steam is discussed. [Display omitted] • Alloy 304HCu was oxidized in AUSC steam at 650 ℃, 31 MPa for 600 hours. • Non-shot peened surfaces form thick Fe-rich oxides and undergo internal oxidation. • AUSC steam causes severe oxidation and early onset of oxide spallation. • Shot-peening resulted in grain refinement and high dislocation density. • Shot-peened surfaces resist Cr 2 O 3 breakdown, form thin, external Cr & Mn-rich oxides. [ABSTRACT FROM AUTHOR]

In this paper, the structural and compositional evolution of the passive films formed on the Mo-containing stainless steels induced by chloride ions in 0.1 mol L−1 NaOH solution has been studied by means of aberration-corrected transmission electron microscopy and X-ray photoelectron spectroscopy. Mo is enriched at the outer layer of the passive film, which is attributed to the induction of Cl-. Moreover, MoO 4 2- is formed due to the alkaline solution, which impedes the film formation process and inhibits the thickening of the film. Consequently, the positive effect of Mo in the passive film on the corrosion resistance is strongly suppressed. [Display omitted] • The evolution of passive film induced by Cl- in NaOH solution is observed. • The passive film is homogeneous in element distribution in alkaline solutions. • The direct experimental evidence for the formation of NiFe 2 O 4 spinel is observed. • Mo incorporated in passive films is induced by Cl- is directly visualized. • The positive effect of Mo is suppressed due to the formation of MoO 4 2-. [ABSTRACT FROM AUTHOR]

Despite extensive research and proposed theories on formation and breakdown of passive layers, several questions remain unanswered. These include the reasons behind the bi-layer nature of the passive layer, the decrease in hydrogen and oxygen diffusivity upon entering the passive layer, and the influence of microstructure on passive layer formation and function in stainless steels. In this study, we employed ReaxFF molecular dynamics simulations to investigate passivation and depassivation of ferritic stainless steels in a polycrystalline structure. Through static and dynamic calculations, we elucidated the underlying mechanisms of passive layer formation, which were primarily governed by clustering. Our analysis also highlighted the significant role of hydrogen diffusion and its reaction with metallic compounds in the depassivation process. We have identified several physical phenomena involved in the processes of passivation and depassivation, which can provide explanations for the questions posed above. [Display omitted] • Clustering and local detachment of metallic atoms are the main drivers behind the formation of passive layers in ferritic stainless steels. • Microstructure, including point defects and extended defects play a critical role in the formation and degradation of passive layers. • Hydrogen plays a crucial role in the diffusion of solution constituents and passive layer breakdown. • Not only the bi-layer character of the passive layer but also its composition gradient can be explained. [ABSTRACT FROM AUTHOR]

This work employed the "dissolution-diffusion-deposition" model to quantitatively describe the effect of N-Mo synergism on passivation process. The model was optimized by calibrating the ion concentration, calculating the equilibrium between H+ and OH−, as well as calculating the formation amount of passive film components. Through modelling studies, we visualized and quantified how N-Mo synergy promoted passivation process. Results demonstrate that N-Mo synergy enhanced corrosion resistance by suppressing acidification of solution, increasing Cr 2 O 3 content and improving cation-selectivity of passive film. The mutual promotion between hydrolysis of NH 3 and transpassive dissolution of Mo oxides played a critical role in improving corrosion resistance. [Display omitted] • The "dissolution-diffusion-deposition" model was optimized to improve reliability. • N-Mo synergy significantly enhanced the corrosion resistance of stainless steel. • Formation processes of passive film on stainless steels with different N and Mo contents were quantitatively studied. • Mutual promotion between NH 3 and MoO 4 2− played a critical role in strengthening passive film. [ABSTRACT FROM AUTHOR]

The effect of surface grinding on the stress corrosion cracking initiation of 316LN stainless steel in 600 °C supercritical CO 2 was studied through constant extension rate tensile test. The ground surface exhibited much higher oxidation resistance than the polished surface as the deformation layer can greatly enhance the diffusion of active elements and promote the formation of more protective oxide scale. Moreover, the intergranular cracking was effectively suppressed on the ground surface as the ingress of oxidant along the original grain boundary was inhibited. [Display omitted] [ABSTRACT FROM AUTHOR]

The corrosion behavior of three austenitic stainless steels with basial composition of 20Cr25Ni (R1, SR1 and R1Al) was investigated in supercritical CO 2 at 650℃. R1 was cold-rolled, SR1 was solution-annealed and R1Al was R1 with aluminum addition. The results indicate that solution annealing enhanced the corrosion resistance, reducing weight gain by 37.9% and mitigating preferential corrosion. Adding aluminum to R1 further improved its corrosion resistance, decreasing weight gain by 75.5% and eliminating preferential corrosion. The oxide film structure of R1 is SiO 2 , Mn 2 O 3 , Cr 2 O 3 from the inside out, while that of R1Al is Al 2 O 3 , Cr 2 O 3 , and spinel oxides. • Three high-Cr stainless steels were prepared, showing great corrosion resistance in SC-CO 2. • Solution annealing improved the corrosion resistance of cold rolled stainless steel. • Al addition modifies the structure of oxide film, significantly improving corrosion resistance. [ABSTRACT FROM AUTHOR]

Stress corrosion cracking (SCC) of laser powder bed fusion 316 L stainless steel in oxygenated high-temperature water environments with chloride addition at 288 °C was studied. The influences of surface finishes (as-built, mechanically polished, Hirtisation® and shot peened), heat treatments (solution annealing at 1066 and 1150 °C and hot isostatic pressing) and the printing orientations on SCC were evaluated. Hirtisation resulted in a lower SCC susceptibility than as-built or polished surface while shot peening showed the lowest apparent SCC resistance. A high annealing temperature decreases SCC resistance. The effect of printing orientation is material and environment dependent. • Effect of surface finish, heat treatment and orientation on SCC of L-PBF 316 L. • SCC resistance of surfaces ranks as Hirtisation ˃ polishing/as-built ˃ shot peening. • SCC susceptibility increased with annealing temperature. • Horizontally printed specimens showed more cracking than vertically printed ones. • Atmosphere and soaking time during HIP significantly affect SCC susceptibility. [ABSTRACT FROM AUTHOR]

Grain boundary engineering (GBE) can effectively improve the corrosion resistance of materials, but the traditional thermal-mechanical process still exhibits some limitations. In the present work, a novel surface spinning strengthening (3 S) technology followed by heat treatment was applied to modify the microstructure near the surface (∼ 400 μm) of a high-N Ni-free austenitic stainless steel. Under an optimal condition of annealing at 1323 K for 60 min after 3 S, the fraction of special boundaries mainly involving Σ3 boundaries in GBE layer was significantly improved from 48.3 % to 69.1 %, thus achieving excellent resistances to intergranular corrosion and stress corrosion cracking. • Surface spinning strengthening technology followed by heat treatment was proposed forward as an effective surface GBE process. • Surface GBE markedly improves corrosion resistance while remaining mechanical strength. • Surface GBE introduces a high fraction of Σ3n boundaries in surface layer and diminishes random high-angle GB connectivity. • Σ3 boundaries greatly hinder the propagation of corrosion cracks along GBs. [ABSTRACT FROM AUTHOR]

Hydrous Cr 2 O 3 and Fe 2 O 3 surfaces without and with substitutional molybdenum were simulated by DFT modelling to investigate at the atomic scale the role of Mo in improving the corrosion resistance of passive films on stainless steels. The surface structures most energetically favoured were determined in the conditions of interest. For surfaces with a high degree of hydroxylation, the preferential location of substitutional Mo is just under the hydroxyl groups, in agreement with the experimental observations. The substitution by Mo is exothermic and Mo preferentially substitutes in Fe- than in Cr-rich zone of the inner barrier layer of passive films. • DFT modelling of (0001) hydrous Cr 2 O 3 and Fe 2 O 3 surfaces to study passivity. • Determination of energetically favoured terminations in the conditions of interest. • Exothermic substitution by Mo more favoured on Fe 2 O 3 than on Cr 2 O 3 surfaces. • Preferential location of Mo on the surface after highly hydroxylation. [ABSTRACT FROM AUTHOR]

In general, δ-ferrite phases, especially in the weld, are not conducive to the hydrogen embrittlement (HE) resistance of austenitic stainless steels (ASSs). However, it is interesting to note that if a ribbon-like δ-ferrite was introduced into ASS, its HE resistance can be improved. In this work, we take 310 S ASS as an example and form a ribbon-like δ-ferrite on the original austenite grain boundary by quenching at 1200℃. This newly formed ribbon-like δ-ferrite phase not only alters the hydrogen enrichment characteristic from austenite grain boundaries to austenite/δ-ferrite interfaces but also contributes to an increased resistance to HE. [Display omitted] • The ribbon-like δ-ferrite can be formed on the austenite grain boundaries of 310S stainless steel by quenching at 1200°C. • The ribbon-like δ-ferrite transforms the hydrogen enrichment from a single-layer interface to a dual-layer characteristic. • The presence of ribbon-like δ-ferrite almost doubles the total hydrogen storage capacity at the grain boundaries. • The hydrogen embrittlement resistance of 310S stainless steel can be improved by introducing ribbon-like δ-ferrite. [ABSTRACT FROM AUTHOR]

The effects of simultaneous lanthanum and nickel addition on the oxidation behavior and area-specific resistance (ASR) of stainless steels for fuelcell interconnects were investigated. The La and Ni addition promoted the entire growth of the oxide layer and increased the roughness of the metal/oxide interface. Despite the thicker oxide scale, these alloys prevented the increase of ASR compared to the alloy with only Ni added. The void analysis indicated that simultaneous La and Ni addition could prevent void growth, leading to lower ASR. The above findings can be interpreted in terms of the fast La diffusion and convoluted metal/oxide interface. • La intermetallic close to La 3 Ni were observed in La and Ni-added alloys. • Liquid diffusion was observed due to the low La intermetallic melting temperature. • The fast La diffusion increases oxide growth and the interface roughness. • Despite the thicker oxide scale, ASR increase is prevented. • The addition of La and Ni prevents void growth and improves scale adhesion. [ABSTRACT FROM AUTHOR]

Though the classical transport theory does not mathematically express the Arrhenius-like relation between Cr-loss flux due to volatilisation and absolute temperature, such relation was experimentally observed for 409L stainless steel exposed at 600–750 °C. Volatilisation calculation in the present cases can be estimated giving such relation because of the nearly linear relation between mass transfer coefficient and temperature. Cr-loss fluxes in O 2 with 20 and 40 % H 2 O are close to or coincided with the fluxes calculated from MnCr 2 O 4 evaporation. Increasing water vapour could enhance volatilisation contributed from the raised CrO 2 (OH) 2 pressure, reduce oxidation rate, and worsen scale adhesion. • 409L stainless steel was assessed at 600–750 °C for SOFC interconnect application. • Flux of Cr loss by volatility related to temperature in the Arrhenius-like form. • Cr-loss flux equation can be simplified resulting in the Arrhenius-like relation. • Water vapour could help reduce oxidation rate with enhanced scale volatilisation. • Water vapour could worsen the scale adhesion. [ABSTRACT FROM AUTHOR]

The impact of 316L stainless steel discolouration on chloride induced pitting corrosion was quantified. Several degrees of discolouration were produces by chemical passivation, simulated rouging or anodic polarization. Discolouration was characterized by spectral analysis in the visible and NIR range (400-1000 nm). Pitting corrosion resistance was quantified by pitting potential measurements. The spectra were used to indicate whether pitting or transpassive behaviour would occur using chemometric classification techniques with 88% accuracy. In addition, pitting potentials were predicted combining chemometrics and survival analysis techniques with a 90 mV RMS error in cross-validation. XPS analysis linked pitting resistance with the Cr/Fe balance. • 316L surface discolouration can be quantified by Vis-NIR spectral measurements. • The occurrence of pitting was predicted by application of chemometric classification. • The pitting potential was predicted by application of chemometric survival analysis. • Transpassive outcomes are included by combining chemometric and survival regression. [ABSTRACT FROM AUTHOR]

N-lauroylsarcosine sodium is proved to be effective in inhibiting 304 L SS pitting corrosion. Under various elastic tensile stresses, the inhibition behavior of N-LSS on 304 L SS pitting corrosion is studied, and N-LSS increases significantly 304 L SS pitting potential by more than 400 mV. Under small elastic tensile stress (≤16.63 %σ 0.2), the adsorption of N-LSS can inhibit 304 L SS pitting corrosion by enhancing the protection of N-LSS film and specific adsorption effect of N-LSS. Under large elastic tensile stress (≥46.84 %σ 0.2), the decrease of N-LSS adsorption effect reduces the inhibition effect of N-LSS specific adsorption for 304 L SS pitting corrosion growth. • N-LSS could effectively inhibit the initiate and growth of 304 L SS pitting corrosion. • The elastic tensile stress has little effect on 304 L SS pitting corrosion initiation. • The elastic tensile stress can affect the adsorption effect of N-LSS. • Elastic stress affects N-LSS specific absorption on 304 L SS pitting corrosion growth. [ABSTRACT FROM AUTHOR]

The flow-influenced corrosion (FIC) behavior of SA106B/316L stainless steel (SS) welded joints with SS located upstream and downstream is investigated experimentally and numerically. The damage components of microstructure heterogeneity and geometric discontinuity are quantified. The FIC of the welded joint is affected by the combination of galvanic corrosion, mass transfer, and charge transfer. The electrochemical measurements indicate that the corrosion is aggravated by a flow disturbance component of 18.70∼26.96%. The corrosion of SA106B carbon steel is more severe than 52M and 316L SS due to galvanic effect, which is further promoted by flow disturbance. The FIC mechanism is also discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Pitting and galvanic corrosion of 2205 DSS with σ phase were investigated in the presence of Pseudomonas aeruginosa. Pitting corrosion was accelerated by σ phase, and further promoted by P. aeruginosa. The σ phase changed the distribution of pitting sites from being concentrated on phase boundaries and α phase in the solution treated coupons to being around σ phase in the biotic medium. The galvanic corrosion between α and γ phases was enhanced by the bacterium, and σ phase led to anodic dissolution of γ phase instead of α phase in DSS with solution treatment. • Pitting corrosion of 2205 DSS is accelerated by σ phase. • Pitting corrosion is further promoted by P. aeruginosa. • Pitting occurs around σ phase due to the initial bacterial attachment. • The α phase corrodes galvanically for DSS with solution treatment. • The σ phase results in the anodic dissolution of γ phase instead of α phase. [ABSTRACT FROM AUTHOR]

The effect of dissolved hydrogen (DH) on the corrosion fatigue crack growth (CFCG) behavior of 316LN stainless steel (SS) was investigated in high temperature pressurized water. The results indicated that DH slightly increased the CFCG threshold stress intensity range (ΔK th) value by 9 % and significantly increased the corrosion fatigue crack growth rate (CFCGR) value by 35 %. On the one hand, DH promoted a large plastic zone formed ahead of the crack tip. On the other hand, DH addition transformed the crack growth mechanism from mainly the slip-dissolution without DH addition to the competition between the slip-dissolution and mechanical fatigue. • DH increased the ΔK th of 316LN stainless steel in water environment. • DH slightly increased the corrosion fatigue crack growth rate in water environment. • DH promoted a large plastic zone formed ahead of the crack tip. • DH significantly affected the corrosion fatigue crack growth mechanism. [ABSTRACT FROM AUTHOR]

Compared to the well-recognition of passivation, the events occurring during transpassivation is insufficiently understood. Here, by means of aberration-corrected transmission electron microscopy, we show that transpassivation induces the oxide film on the 654SMO super austenitic stainless steel thickening to 50–70 nm. Chromium oxide is dominant in the thickened film and distributes homogeneously along the in-depth direction. Metal nitrides is indicated to be formed in the thickened film by the evident incorporation of N with negative valence. This work shows a more possibilities to the film modification by transpassivation than the general consensus that chromium is oxidized to higher-valence soluble ions. [Display omitted] • Transpassivation induces the passive film on the 654SMO thickened to about 50–70 nm. • Transpassivation induces a more homogeneous oxide film in composition distribution. • Transpassivation induces the incorporation of N with negative valence state. • The modified film by transpassivation is more resistant to the chloride attack. • It is proposed that N is responsible for the enhanced transportation property of film. [ABSTRACT FROM AUTHOR]

The corrosion and carburization behaviour of four austenitic stainless steels were evaluated in CO 2 and CO 2 +impurities (CH 4 , CO and O 2) at 600 °C. Exposure to CO 2 , CO 2 +CH 4 , and CO 2 +CO environments showed poor corrosion resistance, especially in 316 grades with the spallation of Cr 2 O 3 layer and breakaway corrosion. Conversely, materials showed improved corrosion resistance in CO 2 +O 2 environment with thin Cr 2 O 3 layer. TEM analysis of 316LN revealed carbon-accumulated layer at the Cr 2 O 3 –matrix interface for highly corrosive environments. The degradation of Cr 2 O 3 adherency is correlated with the carbon-accumulated layer, resulting from the high carbon activity in CO 2 , CO 2 +CH 4 , and CO 2 +CO environments. • Stainless steels were tested in CO 2 , CO 2 +CH 4 , CO 2 +CO, and CO 2 +O 2 at 600 °C. • Poor corrosion resistance was observed in CO 2 , CO 2 +CH 4 and CO 2 +CO environments. • Carbon-accumulated layer observed at Cr 2 O 3 –matrix interface in those environments. • Carbon-accumulated layer affects the adhesion between Cr 2 O 3 layer and matrix. • O 2 impurity prevents carbon-accumulation and provides better corrosion resistance. [ABSTRACT FROM AUTHOR]

This study examined how cold forging (CF) affects the corrosion of 316 stainless steel (SS) in molten FLiNaK salt at 700 °C for 48 h. CF samples had two corrosion areas: one near the top and another displaying intergranular corrosion (IGC). Samples with lower CF (5–30 %) showed more IGC, while the 50 % CF sample had less IGC but the shallowest corrosion depth. This was due to the increased number of grain boundaries, which raised the potential corrosion initiation sites, and certain grain boundaries promoting chromium dissolution, thus enhancing IGC. • In the cold forging (CF)-treated samples the corrosion pattern could be divided into two distinct zones. • A corrosion-concentrated region was found close to the top surface, followed by intergranular corrosion regime. • Lower CF levels (5–30 %) samples exhibited a corrosion-concentrated region, followed by deeper IGC. • While, 50 % CF sample mainly showed a corrosion-concentrated region, and the lowest total corrosion depth. [ABSTRACT FROM AUTHOR]

Stress corrosion cracking behavior of stainless steel 304 L was investigated in full immersion, evaporated artificial sea salt brines (ASW) at 55 °C. It was observed that brines representative of thermodynamically stable brines at lower relative humidity (40% RH, MgCl 2 -dominant) had a faster crack growth rate than high relative humidity brines (76% RH, NaCl-dominant). Observed crack growth rates (da/dt) under constant stress intensity (K) conditions were determined to be independent of transitioning procedure (rising K or decreasing frequency) regardless of solutions investigated for the orientation presented. Further, positive strain rates had little to no impact on the observed da/dt. The observed behavior suggests an anodic dissolution enhanced hydrogen embrittlement mechanism for SS304L in concentrated ASW environments at 55 °C. Additional explorations further examined environmental influences on da/dt. Nitrate additions to 40% ASW at 55 °C solutions were shown to decrease measured da/dt and further additions stopped measurable crack growth. After sufficient nitrate had been added to fully stifle crack growth, a temperature increase to 75 °C induced cracking again, and a subsequent decrease to 55 °C once again stopped da/dt. These tests demonstrate the importance of ascertaining both brine-specific chemical and dynamic environmental influences on da/dt. • Quantitative, in-situ crack growth for stainless steel 304 L in seawater solutions. • MgCl 2 -dominant seawater brines exhibited faster cracking than NaCl-dominant brines. • No strain rate dependence was observed for stainless steel 304 L in seawater. • Nitrate additions to low MgCl 2 -dominant brines ceased crack growth. • Anodic dissolution hydrogen embrittlement mechanism proposed for stainless steel. [ABSTRACT FROM AUTHOR]

The corrosion behavior of 316 stainless-steel with a tantalum (Ta-316) coating deposited using PVD technology was investigated in subcritical environments containing Cl− and Br− at 290 °C and 6 MPa. The corrosion rate of Ta-316 continuously decreased with increasing exposure time, demonstrating its high corrosion resistance. A thin film, mainly composed of Ta 2 O 5 , formed on the surface of the tantalum coating, preventing the diffusion of substrate elements. The corrosion process and mechanism of Ta-316 were also examined. • Corrosion of alloys by Cl- and Br- under subcritical conditions was studied. • The tantalum coating effectively inhibits substrate corrosion. • Outer layers is mainly composed of Ta 2 O 5 , while transition layer is composed of Ni-Fe oxides. • The uniform corrosion induced by Br- trended to be more severe than that induced by Cl- in the short term. [ABSTRACT FROM AUTHOR]

The influence of a severe shot peening (SSP) treatment in corrosion resistance of AISI 316 L austenitic stainless steel was studied by different electrochemical measurements in 3.5% NaCl solution. SSP promoted the formation of ultrafine grains in the upper layer. The formation of strain induced martensite appears to be facilitated by twinning due to the induced severe plastic deformation. SSP treatment with subsequent low temperature annealing (350ºC) improved corrosion resistance. The distinction of corrosion resistance is attributed to the different mechanical and microstructural features caused by severe plastic deformation. The best properties and stability of passive film were corroborated from various electrochemical techniques: potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy. [Display omitted] • SSP induces gradient grain refinement from surface to the core. • SSP promotes the formation of strain induced martensite. • Corrosion resistance decreases after SSP. • SSP with subsequent low temperature annealing enhances corrosion behavior. • Low annealing (350ºC) enhances Cr diffusivity in ultra-fine grained microstructure. [ABSTRACT FROM AUTHOR]

The effect of the Mo element on the intergranular corrosion behavior was investigated on super-austenitic stainless steels. The σ-phase structure and compositional changes of stainless steels with different Mo contents during aging at 800–900°C were investigated by TEM, combined with electrochemical tests, and two different intergranular corrosion mechanisms were revealed. The low-Mo 904 L stainless steel induces severe intergranular electrochemical corrosion due to selective anodic dissolution at grain boundaries caused by decreased passivation ability and σ-phase composition changes. The σ-phase precipitation of 254SMo and AL-6XN with high-Mo leads to Cr and Mo depletion reduces passivation film continuity, and causes intergranular corrosion. • Aging coarsens the σ-phase at grain boundaries in super austenitic steels with higher Mo content. • Low Mo austenitic steels face intergranular corrosion from weakened boundary passivation. • High Mo steels suffer intergranular corrosion from Cr/Mo depletion and erratic passivation. • Precipitate morphology and composition significantly alter intergranular corrosion. [ABSTRACT FROM AUTHOR]

Fretting crevice corrosion at the fastening interfaces of stainless-steel products is an unavoidable issue in the medical, marine, and nuclear industries. In this study, the effects of the fretting regimes on the fretting corrosion in artificial crevices were investigated, and the results showed that fretting initiated severe corrosion inside the crevice under the stick regime. Under the stick–slip and slip regimes, the volume loss was dominated by fretting corrosion, without initiating crevice corrosion. • Whether fretting can cause crevice corrosion is related to the fretting state. • In the stick regime, fretting can initiate severe corrosion inside the crevice. • In the stick–slip and slip regimes, only fretting corrosion occurs inside the crevices. [ABSTRACT FROM AUTHOR]

In this work, a non-steady electrochemical model for assessing stress corrosion cracking (SCC) of 2205 duplex stainless steel (DSS) under applied polarization potentials was proposed, and the SCC mechanism was revealed. With the negative shift of potentials, hydrogen enhances SCC susceptibility by deteriorating passive film, inhibiting repassivation and causing serious damage. In particular, at −850 mV (vs. SCE), the synergetic effect of anodic dissolution (AD) and hydrogen embrittlement (HE) causes severe pitting and SCC. The negative shift of applied potentials changes the preferential pit/SCC initiation site due to high hydrogen concentration in austenite. • A non-steady electrochemical model for assessing SCC of 2205 duplex stainless steel was proposed. • The direct evidence was provided that the synergy of anodic dissolution and hydrogen embrittlement controls SCC. • The negative shift of potentials varies the initiation sites of pits and SCC because of hydrogen enrichment in austenite. [ABSTRACT FROM AUTHOR]

The susceptibility of multipass flux-cored arc welds of STSs 308 L and 316 L to hydrogen embrittlement (HE) was investigated at various temperatures. Cracks predominantly initiated and propagated along the δ-ferrite in the interdendritic region at 25 °C. δ-ferrite served as preferred hydrogen trap sites, and the δ/γ boundary became the stress concentration site. At −100 °C, STSs 308 L and 316 L exhibited high susceptibility to HE owing to strain-induced martensite formation, providing additional hydrogen trap sites and dislocation accumulation. Despite strain-induced martensite actively transformed at −196 °C, the HE disappeared owing to the sluggish diffusion of hydrogen to stress-concentrated areas. • STS 308 L welds showed severe HE susceptibility compared to STS 316 L welds. • Crack occurred along the δ-ferrite in the interdendritic region at 25 ℃. • δ-ferrite in welds trapped hydrogen, causing stress concentration and aggravating HE. • α′-martensite at −100 ℃, aggravated HE by hydrogen traps and dislocation pile up. • HE disappeared at −196 ℃ due to sluggish hydrogen diffusion. [ABSTRACT FROM AUTHOR]

The underlying high-temperature oxidation mechanisms of the heat-resistant austenitic stainless steel with gradient nanostructured surface layer is revealed through systematic analysis of the microstructure and composition. Nanoscale oxide grains and high-density grain boundaries promoted the formation of pronounced spinel oxides, which suppressed elemental diffusion and CrO 3 volatilization. High level of residual stress in the GNS layer facilitated the formation of high-density precipitates at the oxide/matrix interface and grain boundaries, which hindered the growth of oxide scale and reactive elements diffusion. The enhanced high-temperature oxidation resistance resulted from the synergistic combination of spinel oxides, precipitates, and high-density grain boundaries. [Display omitted] • Improved oxidation resistance was the synergy result of spinel oxides, precipitates, and grain boundaries. • Extremely fine oxide grains promoted outward diffusion of Mn and forming thick spinel oxide layer. • Gradient strain induced high-density precipitates formation in the gradient nanostructured layer. • Outward diffusion of reactive elements reduced the thermal stability of nanograins. [ABSTRACT FROM AUTHOR]

Given the high strength of multiphase stainless steel, it is imperative to study its hydrogen embrittlement behavior. However, the understanding of hydrogen-assisted crack initiation and propagation is limited. In this study, we investigate the hydrogen-assisted cracking behavior of multiphase stainless steel through crack analysis, hydrogen permeation test, and hydrogen desorption experiments. Our findings reveal that hydrogen-assisted cracks initiate at the martensite packet boundaries and propagate along the packet boundaries, block boundaries, prior austenite grain boundaries and through ferrite. Additionally, we have elucidated the hydrogen trap sources and proposed a hydrogen-assisted cracking mechanism. • Hydrogen-assisted crack initiates at martensite packet boundaries. • Hydrogen-assisted crack extends in a mode of cleavage, quasi-cleavage, and IG. • Three groups of hydrogen traps have been analyzed in MPSS. • Hydrogen-assisted cracking mechanism of MPSS is proposed. [ABSTRACT FROM AUTHOR]

The oxidation behavior of alumina-forming austenitic (AFA) stainless steels exposed to 600 °C supercritical water (SCW) was studied via several high-resolution characterization techniques. The addition of 1.5–3.5 wt% aluminum (Al) significantly affected the microstructure of AFA alloys compared with Al-free alloys, with the formation and re-distribution of precipitates, including Laves, B2-NiAl, and δ-ferrite. After exposure to SCW, a typical duplex oxide scale was formed on the surface, and the oxide thickness decreased with increasing Al content, which was ascribed to the formation of a protective inner oxide layer. The threshold Al content was determined to be 3.5 wt%, as only the AFA alloy with a 3.5 wt% Al addition formed a distinct alumina scale and exhibited the lowest weight gain. The relationship between the Al content, precipitates, and mechanism of oxide film formation was revealed. In the AFA alloys, the volume fraction of B2-NiAl increased with increasing Al content, resulting in a more continuous alumina film formation. The addition of Al promoted the spheroidization of the needle-like Laves phase, leading to the formation of a protective Si-containing oxide film. Additionally, the higher content of Al addition also favored the formation of the δ-ferrite phase, which formed a slightly thicker but uneven alumina film after exposure to SCW. • Oxidation behavior of AFA alloys with different Al contents in supercritical water is investigated. • The higher the Al content, the better the corrosion resistance of the alloy. • Al addition affected alumina scale formation and precipitation characteristics. • AFA alloy with 3.5 wt% addition form a continuous alumina scale in bi-phasic composition. • Excessive precipitates phases decrease alumina scale continuity, increasing N* Al. [ABSTRACT FROM AUTHOR]

A stepwise galvanostatic method was developed to identify the critical pit stability product, (x‧i) crit , of 316 L stainless steel (SS) as a function of pit depth in 0.6 M NaCl at 25°C. (x‧i) crit for a flat-bottom pit was 80–90% of the (x‧i) value for salt film formation, (x‧i) sf , independent of pit depth. However, the (x‧i) threshold at which the pit propagated with a heterogeneous dissolution interface, (x‧i) crit-het , decreased with increased pit depth. The pit adapted its morphology to maintain the active propagation when (x‧i) was between (x‧i) crit-het and (x‧i) crit. The heterogeneous dissolution mechanism was also evaluated using numerical modelling. • A method was developed to determine the dependence of critical pit stability product on pit depth. • The critical pit stability product, (x‧i)crit remains consistent irrespective of pit depth. • The pit can adapt its morphology to sustain active propagation when (x‧i) is between (x‧i)crit-het and (x‧i)crit. • With an increase in pit depth, (x‧i)crit-het decreases. • The heterogeneous dissolution occurs with an undermined surface at the early stage. [ABSTRACT FROM AUTHOR]

Additions of 1–5 wt% W element enhanced corrosion resistance and mechanical properties of LDED-316 SS. Microstructure characterized the grain refinement and precipitation of ferrite and W-Mo carbides. Mechanical tests showed enhanced tensile strength and hardness of 316–5 W by 37.4% and 30.8%, respectively. Electrochemical tests indicated an increasing pitting potential and polarization resistance of 316–3 W in 3.5 wt% NaCl solution by 0.535 V SCE and 1679 kΩ·cm2, respectively. Corrosion morphology showed the preferential dissolution of ferrite and W-Mo carbides rather than austenite cell. The change in corrosion processes and presence of WO 3 in the passivation film significantly contributed corrosion resistance. • W enhanced both corrosion resistance and mechanical properties of LDED-316. • Ferrite and W-Mo carbides decreased the corrosion priority of austenite cell. • W addition promoted the formation of thicker and compact passivation film. • WO 3 actively contributed to the formation of the passivation film. • Solidification mechanism and corrosion mechanisms were discussed in detail. [ABSTRACT FROM AUTHOR]

The oxidation behavior of austenitic stainless steels with 0 and 2.5 wt% Al exposed to 500–600 °C supercritical water was studied. The oxidation rate-temperature dependence of base steel (0 wt% Al) followed the conventional Arrhenius law, while the alumina-forming austenitic stainless steel (AFA steel, 2.5 wt% Al) exhibited an anomalous oxidation rate-temperature dependence, which is attributed to the special phase transition and oxidation behavior of B2-NiAl precipitates in the AFA steel. • Oxidation behavior of an alumina-forming austenitic stainless steel in 500–600 °C SCW is investigated. • Anomalous oxidation rate-temperature dependence is observed in AFA steel. • AFA steel contains less Ni-rich zones when exposed to higher temperature. • The Ni-rich zones are responsible for the anomalous oxidation rate-temperature dependence. • The morphological differences of Ni-rich zones at different temperature is related to the phase transition of B2-NiAl. [ABSTRACT FROM AUTHOR]

Fretting-crevice-corrosion at the modular interface of artificial joints can cause failure of the joint replacement. In this study, long-term fretting crevice corrosion tests of 316 L stainless steel were carried out at the center of an artificial crevice in a saline solution with and without proteins. The results showed that fretting initiated significant crevice corrosion without proteins and corrosion of large areas was observed in the non-contact area inside the crevice. In the presence of proteins, proteins can migrate into the crevice and block the crevice mouth. The enriched proteins had a lubricating effect and inhibited the occurrence of crevice corrosion. • Fretting within artificial crevices can initiate obvious corrosion reaction • Proteins could migrate into the crevice and accumulate at the crevice mouth. • Lubrication of proteins in wear marks alters the fretting regimes. • Proteins enriched inside the crevice and inhibited corrosion reactions [ABSTRACT FROM AUTHOR]

Passivity breakdown and metastable pitting of stainless steel 316 L was investigated in chloride-containing solution using in-situ microscopy and atomic spectroelectrochemistry (ASEC). X-ray photoelectron spectroscopy revealed the presence of Cl- ions in the outer layer of the passive film. The film was found to undergo dielectric breakdown during anodic polarisation, resulting in the formation of metastable or stable pits. ASEC revealed that Cr and Mo can aid in the early repassivation of 'open' pits, whereas 'undercutting' pits were observed to exhibit delayed repassivation later accompanied by rupture of the perforated cover due to the formation of H 2 gas bubbles inside the pit. • Adsorption of Cl- ions in the passive film outer layer promotes dielectric breakdown during anodic polarisation. • The dielectric breakdown of passive film leads to formation of a pit site with a microscopic flare-up. • Cr and Mo promote early repassivation of open pits. • The formation of hydrogen gas bubble inside small undercutting pits causes bulging and rupturing of perforated pit covers. [ABSTRACT FROM AUTHOR]

This study investigated the corrosion performance of Super 304H in 15–25 MPa/600–700 °C supercritical CO 2 with/without 100 ppm O 2 impurity. Under all conditions, Super 304H formed a protective Cr-rich oxide scale, accompanied by magnetite nodules and Nb-rich oxides. The thickness of the oxide scale and the size of the nodules increase with increasing temperature. Isotope tests with subsequent exposures to C16O 2 /16O 2 and C16O 2 /18O 2 found that O 2 impurity enhances oxidation during the initial stage and reduces carburization to some extent. • 100 ppm O 2 impurities are beneficial in the early stage of oxidation and harmful in the later stage. • Increase in temperature and 100 ppm O 2 impurity reduces carburization. • A thick Cr-rich oxide scale has obvious inhibition on carburization. [ABSTRACT FROM AUTHOR]

This study investigates the influence of mechanical conditions on intergranular corrosion (IGC) in type 304 austenitic stainless steel. Electrochemical potentiokinetic reactivation and oxalic acid etching tests were conducted on specimens under tensile loading and unloading in the elastic-plastic region. The results show that their IGC susceptibility became higher than that of intact specimens. Furthermore, tensile loading during corrosion led to an increase in the IGC susceptibility of plastically deformed specimens. The IGC susceptibility of high-energy grain boundaries (GBs) was increased by elastic and plastic deformation around the GBs. Low-energy GBs exhibited little IGC susceptibility for all mechanical conditions. • Intergranular corrosion tests were done on austenitic stainless steel under tension. • Reactivation rate increased as the mechanical conditions became more severe. • Low-energy grain boundaries have high intergranular corrosion resistance. • Tension raises intergranular corrosion susceptibility of high-energy grain boundaries. [ABSTRACT FROM AUTHOR]

The stress corrosion cracking (SCC) behavior of 316LN stainless steels (SS) weld joint in high-temperature and high-pressure (HTHP) water were investigated by the newly developed HTHP water small punch test. The results indicated that SCC behavior of weld joint were strongly influenced by the inhomogeneous microstructure. Intergranular fracture dominated the SCC process of heat affected zone (HAZ) and partial hardening was believed to be the main reason for the increased sensitivity of HAZ to SCC. All samples exhibited cleavage fracture characteristics, indicating that film-induced cleavage dominated the SCC process of SS and its welded joints in HTHP water. • The SCC behavior of weld joint were strongly influenced by the inhomogeneous microstructure. • Film-induced cleavage dominated the SCC process of SS and its welded joints. • Partial hardening was believed to be the main reason for the increased sensitivity of HAZ to SCC. [ABSTRACT FROM AUTHOR]

The corrosion behavior of VNbTa medium-entropy alloy (MEA) was investigated by electrochemical measurement and first-principles calculation. Due to the synergism of higher bond strength and higher oxygen or OH adsorption heat among constituent elements, the MEA has better corrosion resistance than 316 L stainless steel. The stability passive film was related to the high-valent oxides (V 2 O 5 , Nb 2 O 5 , and Ta 2 O 5). The calculation results show that VNbTa MEA has a high work function and adsorption energy for O, and the formation of initial passive film is mainly determined by the bonding of surface Ta, V atoms and O atoms. • Corrosion behavior of VNbTa MEA is studied in 3.5 wt.% NaCl aqueous solution. • The MEA exhibits a better corrosion resistance than orther M/HEAs and conventional alloys. • Excellent corrosion behavior ascribes to the low dissolution rate at initial stage and the stable passivation layer. • Microscopic mechanism of corrosion behavior is revealed by first-principles calculations. [ABSTRACT FROM AUTHOR]

The underwater direct metal deposition (UDMD) was employed to deposit 316 L stainless steel (SS316L) coatings on NV E690 steel. The chemical composition gradient from monolayer to trilayer SS316L induces an in-situ phase transformation, thereby enhancing the corrosion resistance. The steady-state passive film grew linearly with the applied potential and exhibited a bilayer structure: a high resistivity barrier layer and a low resistivity outer layer. The growth kinetics of the UDMD fabricated SS316L coatings align with the point defect model. Passive film is enriched in Cr while depleted in Fe and Ni, whereas the altered zone is enriched in Ni. [Display omitted] • Corrosion resistance was enhanced by coating SS316L through the UDMD technique. • Quantitatively studied the electrochemical and physical properties evolution of the passive film. • The passive film consists of a high-resistivity barrier layer and a low-resistivity outer layer. • The growth kinetics of the UDMD fabricated SS316L coating aligns with the point defect model. • Passive film is enriched in Cr while depleted in Fe and Ni, whereas the altered zone is enriched in Ni. [ABSTRACT FROM AUTHOR]

The effect of thermal aging (0 h- 15,000 h at 400 °C) on the low cycle fatigue properties of Z3CN20.09M stainless steel was investigated. The micro-hardness of the ferrite increases with thermal aging time, while that of the austenite is almost unchanged. The fatigue life of Z3CN20.09M stainless steel in high-temperature pressurized water decreases with thermal aging time. The fatigue cracks formed everywhere, mainly including at slip bands in austenite, at the δ/γ phase boundary and in ferrite. Thermal aging promotes crack initiation and propagation in ferrite. The effect of thermal aging on the fatigue damage process is discussed. • Spinodal decomposition and precipitation of M 23 C 6 and G phase occurred during thermal aging. • Thermal aging induces embrittlement and degrades corrosion properties of Z3CN20.09M steel. • The fatigue life of Z3CN20.09M steel in high-temperature pressurized water decreases with thermal aging time. • Thermal aging promotes fatigue crack initiation and propagation in the ferrite. [ABSTRACT FROM AUTHOR]

The stress corrosion cracking (SCC) and the electrochemical behavior of 904 L stainless steel in a simulated seawater environment were investigated using slow strain rate testing (SSRT), electrochemical polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) curves. The sensitive potential range of 904 L stainless steel was determined by the fast and slow scan potential polarization curve, is − 950 mV SCE ∼ 270 mV SCE. Moreover, with the negative shift of applied potential, the toughness fracture characteristic of the three kinds of steel is reduced, and the sensitization state steel is the most obvious reduction. Finally, a practical formula for evaluating the SCC susceptibility of 904 L stainless steel was developed by integrating data from SSRT and fast and slow scan polarization curves. [Display omitted] • The decreased applied potential decreased the corrosion resistance and increased the SCC sensitivity of 904L stainless steel. • The SCC mechanism of 904L stainless steel in simulated seawater is mainly the mixing mechanism of AD and HE. • Organization optimization reduces the susceptibility of intergranular corrosion to SCC of 904 L stainless steel. • The SCC susceptibility evaluation formula of 904L stainless steel has been established. [ABSTRACT FROM AUTHOR]

The influence of precipitation on the intergranular corrosion sensitivity of Alloy 31 aged at 950 ℃ for 0–96 h was investigated by microstructure analysis and the modified double loop electrochemical potentiokinetic reactivation method. The results reveal that the kinetics of the primary precipitated sigma phase agree with the Yamamoto equation. The degree of sensitization increases rapidly to 4 h, then decreases to 8 h with self-healing, but no further self-healing occurs after that. The degree of sensitisation depends on the Cr and Mo-depletion zone neighbouring the precipitated sigma phase. [Display omitted] • The precipitation kinetics of the sigma phase agrees with the Yamamoto equation. • The intergranular corrosion sensitization is dependent on the Cr and Mo-depletion region induced by the sigma phase primarily. • The degree of sensitization increases rapidly to 4 h, then decreases to 8 h with self-healing, but no further self-healing occurs after that. [ABSTRACT FROM AUTHOR]

Stainless steel 316 L exposed to LiCl-Li2O molten salt containing Li metal for 500 and 1000 h experiences deep intergranular attack and bulk void formation. This degradation is due to a synergistic corrosion mechanism, different than other forms of molten salt corrosion, where Cr and Mn oxides and carbides form along grain boundaries and are dissolved by Li metal. Synchrotron transmission X-ray microscopy 3D imaging is used to show corrosion morphology and Cr enrichment and depletion in a novel format that has not previously been used for bulk corrosion samples. • Exposure of SS316L to LiCl-Li2O-Li leads to deep intergranular corrosion. • Attack differed from corrosion in molten salt containing no oxide or Li metal. • Synchrotron X-ray microscopy used to construct 3D images of cross section. • A novel metal induced mechanism leads to dissolution of Cr and Mn. [ABSTRACT FROM AUTHOR]

This work focuses on the influence of the feedstock powders on the microstructural properties and corrosion behavior of 316 L stainless steel (SS) produced by laser powder bed fusion (L-PBF) from two different suppliers. Microstructural investigations conducted after additive manufacturing reveal many particularities depending on the powders. These microstructural differences lead to a different corrosion behavior in boiling nitric acid containing oxidizing ions. The presence of the triple structuration (grains, large cells, small internal cells) shows a positive effect on intergranular and cellular corrosion resistance. In both cases, L-PBF 316 L SS provides better resistance to intergranular corrosion than wrought 316L SS. • Impact of raw material properties on the microstructure of 316L SS produced by laser powder bed fusion. • A new triple structuration (grains, large cells and small internal cells) has been evinced. • Printed samples exhibited better corrosion resistance compared to wrought 316L SS in strongly oxidizing acidic medium. • The new microstructure shows a slightly intergranular attack and improves cell corrosion resistance. [ABSTRACT FROM AUTHOR]

This work explores the relation between microstructural features and pitting corrosion resistance of additively manufactured 316 L stainless steel. Specimens fabricated using two different laser-based manufacturing processes (L-PBF and L-DED) were studied in as-built and heat-treated conditions following a comparative approach. Potentiodynamic polarization tests and corrosion morphology analysis served to evaluate their corrosion resistance and passive behavior. This work shows that, contrary to previous reports, the absence of MnS inclusions or presence of the microsegregation structure are not the main factors enhancing passivity of these materials. Instead, dislocation density was the only microstructural feature matching the trend in their passivity behavior. • Passivity follows relation (L-PBF>L-DED>Wrought) for heat treatment bellow 1000 °C. • Heat treatment above 1210 °C deteriorates corrosion resistance by enhancing IGC. • MnS inclusions and micro-segregation structure are not deciding factors in corrosion. • Dislocation density was the only microstructural feature matching trend in passivity. [ABSTRACT FROM AUTHOR]

The martensitic stainless cutlery steel is frequently exposed to conditions where there were both wear and corrosion in the daily usage of kitchen cutlery. To understand the degradation mechanism of the cutlery steel under practical application environments, tribocorrosion tests were performed on 60Cr16MoMA martensitic stainless steel (MSS) in 3.5 wt% NaCl solution and pressed Shanghai Bok Choy (pSBC). The results revealed that compared with 3.5 wt% NaCl solution, the 60Cr16MoMA steel exhibited better tribocorrosion resistance in pSBC during sliding. Through analysis of cross-sectional wear track profiles, it was found that the 60Cr16MoMA steel had the least volume loss when tested in pSBC. High performance liquid chromatography-mass spectrometry results showed that flavonoids and ascorbic acid were present in pSBC, which may act as corrosion inhibitors and stabilize the passive film through physisorption or chemisorption. X-ray photoelectron spectrometer results further confirmed that the passive film formed in pSBC was more stable due to higher Fe2+/Fe3+ and Cr 2 O 3 /Cr(OH) 3 ratios. These findings further confirm the MSS are subjected to the hazards of wear, corrosion and tribocorrosion, and provide important empirical and theoretical support for evaluating cutlery steel volume loss in practical application environments in the future. • Tribocorrosion behavior of martensitic stainless cutlery steel was studied in actual food solution Shanghai Bok Choy. • Pitting potential in Shanghai Bok Choy is higher than 3.5 wt% NaCl. • 3.5 wt% NaCl lead to a higher volume loss than Shanghai Bok Choy. • 3.5% NaCl tests give more severe tribocorrosion attack than Shanghai Bok Choy. • Flavonoids and ascorbic acid in Shanghai Bok Choy stabilize the passive film on the steel surface. [ABSTRACT FROM AUTHOR]

The dissolution–ionization–diffusion–deposition (DIDD) model was used for developing a corrosion–resistant stainless steel (SS) by the means of alloying and the guidelines for the process were proposed. The novel HP–13Cr–Cu SS was designed to resist corrosion in H 2 S–containing geothermal environment. The results indicated that the preferential deposition of CuS promoted the heterogeneous nucleation rate of Cr 2 O 3 , FeCr 2 O 3 , and FeS, which formed denser corrosion product layer. As a result, this alloy exhibited a low corrosion rate and a high sulfide stress cracking (SSC) resistance. The results were consistent with the theoretical calculation conducted by the DIDD model. • The DIDD model established the bridge between thermodynamics and kinetics of electrochemical corrosion. • The guidelines for designing corrosion–resistance stainless steel were proposed by means of micro–alloying. • A novel HP–13Cr–Cu SS was designed based on the DIDD model to resistant the H 2 S corrosion. • The testing results verified HP–13Cr–Cu SS gained the low corrosion rate and high SSC resistance. [ABSTRACT FROM AUTHOR]

Two types of 9% Cr heat resistant steels were used to investigate the preferential dissolution mechanism of Laves phase in 8 mol/L NaOH solutions in an atomic scale by quasi-in-situ TEM analyses and first principles calculations. The dissolution of Laves phase is due to the unprotective oxide film. The dissolution rate of Laves phase was associated with the crystal orientation, and the stacking faults hinder the dissolution of Laves phase in a strong alkaline solution. Further, DFT calculations were used to illustrate the dissolution process of Laves phase, and the result is consistent with the TEM observation. • The dissolution of Laves phase is due to the unprotective oxide film. • The dissolution rate of Laves phase was associated with the crystal orientation. • The stacking faults hinder the dissolution of Laves phase. [ABSTRACT FROM AUTHOR]