不同应力条件下不锈钢局部腐蚀行为的研究进展

不锈钢因具有良好的耐腐蚀性能而倍受重视,在众多工业领域内被广泛使用,但在实际应用中,由于受到腐蚀环境和应力的共同作用,不可避免地会产生点蚀或裂纹,导致服役性能下降,甚至引发各类安全事故.所以,应力条件下不锈钢的腐蚀行为一直是不锈钢材料腐蚀领域的重要研究课题.总结了部分代表性的不锈钢材料在应力作用下局部腐蚀行为的研究进展,主要总结与讨论了弹性应力、塑性应力以及残余应力对不锈钢点蚀及腐蚀开裂行为的影响规律.弹性应力如何影响不锈钢点蚀与腐蚀开裂还不是特别清楚,一般认为弹性拉应力会促进点蚀的萌生,使点蚀坑内产生应力集中,促进腐蚀扩展,但也发现了较小弹性拉应力会抑制点蚀的情况,而且机理也尚不明确,并且弹性压应力到底是促进还是抑制点蚀萌生也尚未达成一致.塑性应力对不锈钢局部腐蚀的影响机理已经比较明确,塑性应力会导致位错的产生,从而促进点蚀和裂纹的生长.残余拉应力会促进不锈钢点蚀和裂纹的生长,但残余压应力却能够有效抑制不锈钢点蚀和裂纹的生长.因此,在较低至中等弹性应力下的不锈钢局部腐蚀行为及其影响机理应该加强研究,而对于塑性应力与残余应力,则应该进一步深入探讨其作用下不锈钢局部腐蚀行为的各阶段特征和断裂临期特征,以期精确进行腐蚀断裂风险的评估和解决寿命评估的难题.

Research Progress on Localized Corrosion Behavior of Stainless Steel under Different Stress Conditions

Due to its good corrosion resistance, stainless steel is widely used in many industrial fields. But in practical application, due to the joint action of corrosion environment and stress, pitting corrosion or cracks inevitably occur, thus leading to the decline of service performance, and even various safety accidents. Therefore, the corrosion behavior of stainless steel under stress has always been an important research topic in the field of stainless steel corrosion. In this paper, the research progress of localized corrosion behavior of some representative stainless steel materials under stress is summarized, and rules and causes of the influences of elastic stress, plastic stress and residual stress on pitting corrosion and corrosion cracking behavior are concluded. Till now, it is not particularly clear how elastic stress affects pitting corrosion and corrosion cracking of stainless steel. Generally, It is believed that elastic tensile stress will promote the initiation of pitting corrosion, which will lead to stress concentration in corrosion pits and promote corrosion propagation. However, it is also found that small elastic tensile stress can inhibit pitting corrosion, and its mechanism is not clear now. In addition, whether elastic compressive stress promotes or inhibits pitting corrosion initiation has yet to be agreed. The mechanism of the influence of the plastic stress on the localized corrosion of the stainless steel has been clarified. Plastic stress can lead to dislocation, thus promoting the pitting corrosion and crack growth. The residual tensile stress can promote the pitting corrosion and crack growth of stainless steel, but the residual compressive stress can effectively inhibit the pitting corrosion and crack growth. Therefore, the study on the localized corrosion behavior and its influence mechanism of stainless steel under low to medium elastic stress should be strengthened. For plastic stress and residual stress, characteristics of various stages and fracture impending characteristics of localized corrosion behavior of stainless steel should be further studied for the purpose of accurately assessing the risk of corrosion fracture and solving the problem of life assessment.