不锈钢应力腐蚀敏感性和钝化膜引起的应力随电位变化的一致性

CONSISTENT VARIATION OF STRESS CORROSION CRACKING AND PASSIVE FILM-INDUCED STRESS FOR STAINLESS STEEL WITH POTENTIAL

奥氏体不锈钢在沸腾 ＭｇＣｌ２溶液中将形成钝化膜．拉伸试佯成膜之前的流变应力和成膜后屈服应力之差就是作用在整个试样上的平均膜致应力．用３０４不锈钢（１Ｃｒ１８Ｎｉ０）测量了在不同电应下的沸腾ＭｇＣｌ２溶液中形成钝化膜所产生的膜致内应力 ．与此同时， 甲慢应变速率拉伸法测量了下同恒电位下的应力腐蚀敏感性． 结果表明，如电位Ｖ≤－５５０ ｍＶｓｃＥ，则钝化膜产生压应力．且下发生应力腐蚀，当电位Ｖ≥－５００ ｍＶｓｃＥ后．钝化膜产生拉应力，已随电位升高、应力增大， 应力腐蚀敏感性也随膜致拉应力升高而增大．因此，３０４不锈钢在沸腾 ＭｇＣｌ２溶液中应力腐蚀敏感性随外电泣的变化和腐蚀钝化膜引起的内应力随外电位的变化完全一致．

The flowing stress of a specimen of type 304 stainless steel (1Cr18Ni9) before unloading is different from the yield stress of the same specimen after unloading and forming a passive film through immersing in a boiling MgCl2 solution at various constant potentials. The difference is the passive film-induced stress. The film-induced stress and susceptibility to stress corrosion cracking (SCC) in the MgCl2 solution at various potentials were measured, At open-circuit potential and under anodic polarization. Both filin-induced tensile stress sigma(P) and susceptibility to SCC I-sigma have maximum values. The film-induced stress and SCC susceptibility, however, decreased steeply with a decrease in potential tinder athodic polarization. When the cathodic potential V less than or equal to-550 mV(SCE), the film-induced stress became compressive. correspondingly, the susceptibility to SCC was zero. Therefore. the variation of filin-induced stress with potential is consistent with that of susceptibility to SCC with potential. A large film-induced tensile stress is the necessary condition for SCC of 304 stainless steel in boiling MgCl2 solution.