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Abstract: Effect of H2S partial pressure on the tensile properties of A350LF2 steel with and without pre-immersion was investigated by slow strain rate testing and electrochemical impedance spectroscopy. The results show that relative tensile strength and plasticity loss increased with increasing in the absence and presence of pre-immersion. Greater tensile property damage occurred in steel without pre-immersion compared to that with pre-immersion. The relative plasticity loss increment of steel without pre-immersion was larger than that with pre-immersion as was increased from 0.1MPa to 1.6MPa. Fractography exhibited flat brittle fracture on the samples without pre-immersion and mixed ductile-brittle fracture on the pre-immersed samples. Furthermore, the embrittled regions on the fracture surface of pre-immersed specimens increased with . In addition, no cracks existed in the steel after pre-immersion. The cracks on the fracture surface of steel could be attributed to the combination of tensile stress and high hydrogen concentration induced by the hydrogen diffusion and accumulation during the tensile test. [Copyright &y& Elsevier]

Highlights: [•] Tensile and impact behavior of the steel had different change law with H2S pressure. [•] Charpy absorbed energy exhibited no obvious change with increasing H2S pressure. [•] Fractography showed mixed ductile–brittle rupture for the corroded mechanical samples. [•] Hydrogen has a profound effect on the tensile and impact behavior of steel. [•] A probable mechanism is proposed to interpret the tensile and impact results. [Copyright &y& Elsevier]

Abstract: The effect of immersion time on the hydrogen content and tensile properties of A350LF2 steel exposed to hydrogen sulphide environments was investigated by immersion tests, hydrogen content measurements and tensile tests. The results show that both hydrogen content and relative tensile strength and plasticity loss increased first and then decreased with increasing immersion time. High mass transfer resistance of corrosion films can be responsible for that hydrogen content decreased after 240h immersion. A probable mechanism is proposed to interpret the reason for hydrogen content result. The tensile property loss and embrittled region were closely associated with hydrogen content. [Copyright &y& Elsevier]

Abstract: The tensile properties and fracture behaviour of A350LF2 steels after exposure to wet H2S environments were investigated by corrosion and tensile testing. The results suggest that relative tensile strength and plasticity loss increased as hydrogen concentration increased. Greater tensile property damage occurred in steel that contained more large-size inclusions. When hydrogen was released, the degree of relative strength and plasticity loss decreased. Fractography of the corroded samples exhibited mixed ductile–brittle rupture. Fractured areas with quasi-cleavage features increased with increasing hydrogen concentration. Flakes appeared in the steel with a low sulphur content and low hydrogen concentration. [Copyright &y& Elsevier]

Present research reports the effect of nano-scale martensite (αʺ) and β phase on the passive film formation and electrochemical corrosion behaviour of Ti-10V-2Fe-3Al alloy in the 3.5% NaCl solution. Nanocrystals with different αʺ/β phase proportion were obtained by room temperature (RT) and Low temperature (LT) burnishing processing. The results show that nano-scale martensite and β phase could promote the growth of passive film and the diffusion of element V, respectively. Corrosion resistance of Ti-10V-2Fe-3Al alloy was enhanced due to the presence of passive film with large thickness and stability, resulting from nano-scale martensite and more β phase in the alloy. Combined with the results of passive film and electrochemical corrosion, a probable mechanism is proposed to interpret the influence of nano-scale martensite (αʺ) and β phase on the passive film formation and corrosion behaviour of Ti-10V-2Al-3Fe titanium alloy. [ABSTRACT FROM AUTHOR]

The effect of H 2 /CO 2 partial pressure ratio on the tensile properties of X80 pipeline steel in the absence and presence of water were investigated by slow strain rate test (SSRT) and scanning electron microscope (SEM) measurements in this paper. The results show that the tensile strength and elongation to failure of X80 pipeline steel in H 2 /CO 2 atmosphere were deteriorated significantly. The relative tensile strength and plasticity loss of X80 pipeline steel increased with increasing H 2 /CO 2 partial pressure ratio in the absence of water. The increasing volume fraction of hydrogen gas is the key influencing factor in this condition. For the H 2 /CO 2 environments in the presence of water, the relative tensile property loss decreased first and then increased with H 2 /CO 2 partial pressure ratio. The probable reason is that the corrosion process changed gradually from CO 2 -dominant to H 2 -dominant. Water played a significant role in the tensile property damage of X80 pipeline steel in the H 2 /CO 2 environments. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of oxide inclusion-induced pitting corrosion in 316L stainless steel exposed to sulphur environments containing chloride ions was investigated by scanning electron microscope analysis, electrochemical measurements and scanning Kelvin probe force microscopy (SKPFM). Two inclusion types were observed. The (Mg,Al,Ca)-oxide inclusions play an important role in pitting formation. SKPFM measurement results show that the inclusion sites exhibited a lower surface potential than the matrix. Finally, the schematic representation of the initiation and propagation process of the (Mg,Al,Ca)-oxide inclusion-induced pitting corrosion in 316L stainless steel exposed to sulphur environments containing chloride ions was established. [Copyright &y& Elsevier]

The influence of H 2 S interaction with prestrain on the mechanical properties of high-strength X80 steel was investigated by slow strain rate tensile tests and hydrogen content measurements. Results showed that elongation to failure first decreased and then increased with increasing prestrain. Moreover, hydrogen content decreased but the relative hydrogen embrittlement(HE) susceptibility, determined by measuring the relative reduction in failure time, increased as H 2 S introduction changed from the origin to the plastic stage. Fractography exhibited brittle fracture for H 2 S-introduced specimens and necking phenomenon decreased significantly compared with H 2 S-free specimens. Secondary cracks in the lateral fracture surface increased with increasing prestrain, indicating higher HE susceptibility. The observations were discussed on the basis of the hydrogen-enhanced decohesion mechanism, H 2 S interaction with prestrain was closely associated with mechanical property degradation. [ABSTRACT FROM AUTHOR]

Tensile properties and fracture behavior of X80 pipeline steel exposed to corrosion environments with different H 2 S/CO 2 partial pressure ratios were investigated through slow strain rate tests (SSRT). The results show that the tensile properties of X80 steel were damaged in H 2 S/CO 2 environments. The tensile strength and elongation to failure of X80 steel decreased significantly with increasing H 2 S/CO 2 partial pressure ratio. The fracture appearance of the corroded samples exhibited mixed ductile–brittle rupture. Fractured areas with quasi-cleavage features increased as H 2 S/CO 2 partial pressure ratio increased. Different types of secondary cracks can be identified on the SSRT specimens in the corrosion environments with different H 2 S/CO 2 partial pressure ratios. [ABSTRACT FROM AUTHOR]

The tensile and impact properties of X70 pipeline steels exposed to wet H 2 S environments were investigated by corrosion and mechanical testing. The results suggest that the Charpy absorbed energy, tensile strength and reduction in area of X70 steel decreased after H 2 S corrosion. When hydrogen was released, Charpy absorbed energy and reduction in area exhibited a certain recovery. Fractography of the tensile and impact specimens exhibited mixed ductile–brittle rupture after corrosion and hydrogen release. Fractured areas with brittle features diminished after hydrogen release. Hydrogen was closely associated with mechanical property degradation and fracture features. [ABSTRACT FROM AUTHOR]

• Cr 23 C 6 precipitates in Fe-9Cr were refined and spheroidized by Mo addition, while Mo/Ni addition had no effect on Cr 23 C 6. • Adding (Mo, Mo/Ni) to Fe-9Cr accelerated chromia formation and improved the oxidation resistance. • The cracks were observed in the scale of Fe-9Cr and Fe-9Cr-1Mo, but not the Fe-9Cr-0.5Mo-0.5Ni. • High-temperature strength of Fe-9Cr was enchanced by alloying elements (Mo, Mo/Ni). Fe-9Cr, Fe-9Cr-1Mo and Fe-9Cr-0.5Mo-0.5Ni (wt%) alloys have been prepared for studying the effect of (Mo, Mo/Ni) on carbide precipitation, oxidation behavior and high-temperature tensile property of Fe-9Cr alloy. Rod-shaped Cr 23 C 6 precipitates in Fe-9Cr alloy were refined and spheroidized by Mo addition, while Mo/Ni addition had no impact on Cr 23 C 6 precipitates. Adding (Mo, Mo/Ni) to Fe-9Cr alloy reduced inward oxygen diffusion and the growth rate of an inner Cr-rich layer, thereby accelerating chromia formation and improving the oxidation resistance. High-temperature strength of Fe-9Cr alloy was also enhanced by alloying elements (Mo, Mo/Ni). [ABSTRACT FROM AUTHOR]

• Cation-selective troilite can restrain corrosion. The corrosion rates are low, and uniform corrosion occurs. • Anion-selective pyrrhotite causes high corrosion rates and localized corrosion. • Crystal atom stacking models of troilite and pyrrhotite are built. • First principle calculation shows troilite surface can attract cations and pyrrhotite surface can attract anions. • The effects of alloy elements on H2S corrosion behaviors are analyzed. H 2 S corrosion behaviors of P110, Fe-Mn-Al, and Fe-Mn-Cr-Ni high-Mn steels were analyzed according to ion-selectivity of corrosion products. At 60 ºC and 80 ºC, cation-selective troilite restrain diffusion of corrosive ions to the substrate. The corrosion rates were low, and uniform corrosion occurred. At 100 ºC and 205 ºC, anion-selective pyrrhotite caused accumulation of Cl− between corrosion scale and substrate. Corrosion rates were high and localized corrosion happened. Crystal atom stacking models of iron sulfides were built, and the adsorption energy of ions on the exposed surface was calculated to discuss the ion-selectivity mechanism. The effect of alloy elements on corrosion behavior was analyzed. [ABSTRACT FROM AUTHOR]