304不锈钢在高温水中的应力腐蚀破裂SCIEI

采用U型弯曲法应力腐蚀破裂试验、电化学测量以及Auger电子能谱(AES)分析方法研究了温度、氯离子浓度和溶解氧含量在高温水中对304不锈钢的应力腐蚀破坏(SC)敏感性的影响及其与表面膜之间的关系。在空气饱和的高温水中(溶解氧为8ppm),随着温度的升高(200—300℃)或氯离子浓度的降低(500—20ppm)304钢SCC敏感性降低。文中还讨论了氧化膜在SCC萌生和扩展中的作用。

STRESS CORROSION CRACKING OF 304 STAINLESS STEEL IN HIGH TEMPERATURE WATER

The correlation of the surface films with the effects of temperature, Cl~- concentration and dissolved oxygen content on the SCC susceptibility of type 304 stainless steel in high temperature water was studied with the aid of U-bend SCC testing and electrochemical measurement as well as AES analysis. With increas- ing temperature, the decreased susceptibility to SCC in air-saturated water contain- ing 100 ppm Cl~- was related to the increase in Cr-enrichment degree in the surface film and to the thickening of the Cr-enriched oxide layer. The increase in SCC sus- ceptibility with increasing Cl~- was attributed to the reduction of Cr content in the oxide film and to the decrease in thickness of the Cr-enriched layer. Lower SCC susceptibility observed at both high and very low dissolved oxygen levels could not simply be related to the change in composition and thickness of oxide films and might be explained by the electrochemical behaviour of Cr and Fe. The role of oxi- de films in initiation and propagation of SCC is discussed.