The features and mechanisms of hydrogen embrittlement of metals that undergo hydride formation and martensitic transformation during service are reviewed. Metastable austenitic stainless steels, Nb and V as well as Ti and its alloys are the metals examined. The embrittlement of austenitic stainless steels is susceptible to the stability of austenite, and hydrogen promotes the martensitic transformation forming hydride as a precursor. However, martensite per se is not always the origin of the embrittlement, but.lattice defects associated with dislocation dynamics in the crack front is noted as a factor. In Nb and V, stress-induced hydride formation successively taking place at the crack front supplies a crack path with a reduced resistance for growth. In Ti, the primary role of hydrides is not always the case. In superelastic and shape memory Ni-Ti alloys, the embrittlement appears prominent in the martensitic transformation, and some dynamic process invoking lattice defects is suggested to play a role. In an appendix, the assessment of the susceptibility in terms of the critical hydrogen concentration is critically discussed, and some mechanical response to hydrogen is proposed as new criteria for the susceptibility of materials to hydrogen embrittlement.
NSSC270 stainless steel is recognized as one of stainless steels that can be used in very severe corrosion environments and it is standardized as SUS312L in JIS (Japan Industrial standard). In this report, corrosion resistance and application examples of super stainless steel, NSSC270(20%Cr-18%Ni-6%Mo-0.8%Cu-0.2%N) with high corrosion resistance and good weldability are mainly described in food industries, desulfurization plants, inner sheets of stack and marine environments. NSSC270 can be manufactured as variety of shapes such as plates, sheets, tubes, bolts, nuts and flanges et al. and delivered within short time.
A new voltammetric method using a strongly alkaline electrolyte (6 M KOH+1 M LiOH) as the supporting electrolyte was applied for simultaneous determination of copper oxides and sulfides. It was found that the reduction peak of Cu2S was well separated from those of copper oxides and appeared at a somewhat higher potential than that of Cu2O. Unlike in the case of the reduction of CuO, CuS was reduced in a stepwise manner. The amounts of Cu2S formed on Cu plates were determined by the LSV method and found to agree well with the values determined by ICP-OES. In the voltammetric measurement of a copper plate in 6 M KOH+1 M LiOH containing S2−, the existence of Cu2S could be confirmed by the emergence of its redox peak pair. The proposed voltammetric method enables the quantitative estimation of a Cu2S film of a few nm thickness formed on Cu. In addition, Cu9S5 could be detected by its reduction peak appearing at a potential slightly higher than Cu2S.