EFFECT OF TRACE-ELEMENTS P AND SI(MN) ON HYDROGEN EMBRITTLEMENT OF JBK-75 ALLOY

High purity hot hydrogen charging at high temperature was used to inve stigate the hydrogen embrittlement (HE) of JBK-75 alloys with differen t contents of P and Si(Mn). The results indicated that by lowering P c ontent, the size and distribution of gamma' precipitate became more ho mogeneous and the precipitation of stable phase eta was retarded, thus the hydrogen resistant properties of the alloy was obviously improved ; however, when Si(Mn) content was lowered together with P, though the size and density of gamma' were also homogeneous and no eta phase was observed, formation of some micro twin around grain boundaries was fo und to be detrimental to the hydrogen performance of the alloy, and hy drogen induced loss of area reduction was very high. Therefore, to imp rove the hydrogen resistant properties of the alloy, P content should be lowered while certain amount of Si(Mn) should be kept.