通过腐蚀速率的测量和腐蚀形貌的SEM观察, 结合点蚀形态的统计分析和点蚀内部及周围应力分布的有限元(FE)分析, 研究了静水压力和预加载拉伸应力对新型Ni-Cr-Mo-V高强钢在模拟深海环境中的腐蚀行为的影响. 结果表明, 随静水压力和预应力的升高, Ni-Cr-Mo-V高强钢的腐蚀速率增大, 表现在点蚀的萌生、发展和合并过程. 静水压力促进了点蚀微孔的萌生和在高强钢表面的随机分布. 静水压力和预应力在点蚀的生长过程中表现出了交互作用, 这在高预应力水平下更加显著. 静水压力以促进点蚀沿平行于表面的生长为主, 预应力是使点蚀深度增大的要素. 点蚀易于沿垂直于预应力方向合并. 随着静水压力和预应力的升高, 点蚀径深比增大, Ni-Cr-Mo-V高强钢向均匀腐蚀转变.

The efforts on deep sea exploration and development have posed many challenges on the corrosion resistance and safety use of high strength steel in recent years. This has attracted a lot of attentions on the corrosion behavior of high strength steel in deep sea environment. Hydrostatic pressure has been identified as one of the most significant factors that affect pitting corrosion of materials or steel structures used in deep sea. However, pre-stress introduced by the actual service conditions is probably another critical factor of deep sea corrosion. The purpose of this work is to investigate the corrosion behavior of a new type Ni-Cr-Mo-V high strength steel under the combined stresses of hydrostatic pressure and preloaded tensile stress in simulated deep-sea environment. Corrosion rate measurement, SEM observation, statistical analysis of pitting geometry and finite element (FE) analysis were used in this work. The results indicated that corrosion rate of Ni-Cr-Mo-V high strength steel increased with the increase of hydrostatic pressure and pre-stress. The deterioration of corrosion resistance of the steel mainly reflected in pit initiation, pit growth and pit coalescence. Rather than pre-stress, hydrostatic pressure exhibited obvious effect on promoting pit initiation. Pits initiated in the form of corrosion pin-holes, which randomly distributed at the corroded surface. Both hydrostatic pressure and pre-stress facilitated pit growth, and there was an interaction between them, which was more remarkable at higher pre-stress. Hydrostatic pressure was mainly responsible for pit growth parallel to the steel surface, while pre-stress was essential to pit depth increase. Adjacent pits were inclined to coalesce in the direction perpendicular to pre-stress. With the increase of hydrostatic pressure and pre-stress, the aspect ratio of pits increased, which can lead to the formation of uniform corrosion.