加铜4Cr16Mo马氏体不锈钢在应力作用下的腐蚀研究

Corrosion Behavior of 4Cr16Mo Martensite Stainless Steel with 1%Cu Addition by Applied Stress

采用应力腐蚀实验方法,对比研究了添加1%Cu的4Cr16MoCu及4Cr16Mo两种材料在3.5%NaCl溶液中的耐蚀性能。结果表明,在低温250℃回火后,两种材料的耐蚀性能没有明显差异,但在600℃高温回火后,4Cr16MoCu材料的耐蚀性能显著增强,通过微结构分析推测,这与富铜相析出有关。通过腐蚀形貌及腐蚀形貌发展过程分析提出此材料在应力腐蚀下的腐蚀发展模型,即在腐蚀初期由于钝化膜破裂引起表面阴阳极区分,形成类电解抛光效应剥离表面钝化膜后进一步形成点蚀。

The corrosion resistance of 4Cr16Mo martensite stainless steels without and with 1%Cu addition(i.e.,4Cr16MoCu)in 3.5%NaCl solution was comparatively studied by three-point flexural loading stress corrosion test method.The results show that there is no significant difference in corrosion resistance between the two steels after tempering at 250℃.However,after tempering at 600℃,the corrosion resistance of 4Cr16MoCu steel is significantly enhanced.Through microstructure analysis,it is speculated that this is related to the precipitation of the Cu-rich phase.A stress corrosion model for the 4Cr16MoCu steel is proposed based on the characteristics and evolution process of corrosion morphology of the steel,i.e.,in the early stage of corrosion,breaks of the passivation film may induce the emerging discrete anode-and cathode-spots on the steel surface,further result in an electrolytic polishing-like effect to peel off the surface passivation film and finally the pitting corrosion.