晶粒尺寸梯度分布对316L不锈钢耐腐蚀性能的影响

Effect of gradient distribution of grain size on corrosion resistance of 316L stainless steel

采用表面机械碾压处理,在316L不锈钢表面制备出纳米晶-粗晶梯度过渡结构,对纳米晶、梯度区和粗晶区样品分别进行化学浸泡实验和电化学腐蚀实验,测试其腐蚀速率、腐蚀电位和点蚀电位等腐蚀性能参数,并对不同状态样品上钝化膜的形态、元素组成、织构及残余应力进行分析,研究晶粒尺寸梯度分布对316L不锈钢耐腐蚀性能的影响。结果表明,纳米晶和粗晶样品浸泡20 h出现稳定腐蚀坑,而梯度区样品浸泡50 h依然保持表面完整。腐蚀电位从纳米晶的-230 mV提高到梯度区的-4 mV,同时腐蚀电流从纳米晶的0.137 A/cm^(2)下降到0.036 A/cm^(2)。晶粒尺寸梯度分布不改变钝化膜形成动力学,梯度区表面钝化膜优异的耐蚀性能与其形成厚度较大、较完整致密且残余应力较小的钝化膜有关。

A gradient nanostructure with grain size varied from nanocrystals to coarse grains was prepared on the surface of 316L stainless steel by surface mechanical grinding treatment(SMGT).The corrosion resistance of the gradient sample was measured by chemical immersion experiment and electrochemical corrosion test,and the effect of gradient grain size distribution on corrosion resistance of 316L stainless steel was analyzed.The results show that stable corrosion pits appeared in the nanocrystalline and coarse-grained samples after 20 h immersion,while the surface of the gradient samples remained intact after 50 h immersion.Electrochemical tests show that the corrosion potential of the gradient sample was enhanced from-230 mV(nanocrystalline sample)to-4 mV.Meanwhile,the corrosion current density decreased from 0.137 A/cm^(2) to 0.036 A/cm^(2).The grain size gradient distribution does not change the kinetics of passivation film formation.The excellent corrosion resistance of the gradient sample originates from the higher thickness and integrity,lower residual stress of the passivation film.