采用表面机械滚压处理(SMRT)在Z5CND16-4马氏体不锈钢上制备出梯度纳米结构(GNS)表层. 利用SEM和TEM研究了GNS表层的组织特点. 结果表明: 晶粒尺寸随深度的增大由最表层的25 nm逐渐增加到基体的原始尺寸, 整个组织细化层的厚度约为150 mm. 对比研究了SMRT样品与原始样品在3.5%NaCl (质量分数)水溶液中的电化学腐蚀行为, 发现点蚀击破电位由原始样品的0.179 V提高到0.313 V, 自腐蚀电位也有所提高. 分析表明, GNS表层中晶粒尺寸纳米化、组织均匀性提高、残余压应力的产生以及表面光洁度的提高有利于其耐点蚀能力的提高.

A gradient nanostructured (GNS) surface layer was fabricated on a Z5CND16-4 martensitic stainless steel by means of surface mechanical rolling treatment (SMRT). The microstructure in the GNS surface layer was characterized by using SEM and TEM. The results showed that the mean grain size increases with depth, from about 25 nm at the topmost surface layer to the initial value in the matrix. The total thickness of the grain-refined layer is about 150 mm. The electrochemical corrosion property of the SMRT sample was compared with that of the as-received sample in a 3.5%NaCl aqueous solution. It is shown that the pitting corrosion potential increases from about 0.179 V in the as-received sample to about 0.313 V in the SMRT sample, and the self-corrosion potential also increases evidently. The formation of nanostructures, the increased structural homogeneity, and the introduction of compressive residual stresses in the GNS surface layer, as well as the decreased surface roughness, were discussed to promote the pitting corrosion resistance of the SMRT sample.