高锰钢和9Ni钢在模拟海水中的应力腐蚀行为对比研究

Comparative Study on Stress Corrosion Behavior of High Manganese Steel and 9Ni Steel in Simulated Seawater

为了研究一种新型海工用高锰钢的耐海水应力腐蚀性及其腐蚀机理,采用慢应变速率拉伸(SSRT)测试了高锰钢和9Ni钢在3.5%NaCl溶液中的应力腐蚀开裂(SCC)敏感性,对比研究了试样的显微组织、电化学行为、SSRT性能、断口形貌特征和裂纹扩展规律。结果表明:2种钢在腐蚀介质中的延伸率、断面收缩率和断裂过程吸收的能量均低于空气介质中的。高锰钢的应变能密度比偏离1更远,综合应力腐蚀指数I_(SSRT)也更大,表现出更高的SCC敏感性。试样在空气中的断口形貌均表现出韧窝-微孔型的韧性断裂特征。在溶液中9Ni钢的SSRT断口形貌表现出典型的韧性-脆性混合断裂特性,而高锰钢呈现明显的穿晶准解理型脆性断裂特征。预拉伸变形试样中高锰钢表现出更大的腐蚀电流密度和更负的腐蚀电位,Mn提供了很强的晶界偏析效应容易引起穿晶SCC。高锰钢的SCC机制可归因于氢致开裂型(HIC)和阳极溶解型(AD)的联合作用。

In order to study the seawater stress corrosion resistance and corrosion mechanism of a new type of high manganese steel used in marine engineering,the stress corrosion cracking(SCC)sensitivity of high manganese steel and 9Ni steel in 3.5%NaCl solution was tested by slow strain rate tension(SSRT).The microstructure,electrochemical behavior,SSRT performance,fracture morphology features and crack propagation law of the samples were compared and studied.Results showed that the elongation,reduction of fracture surface area and energy absorbed during fracture of the two steels in corrosive medium were all lower than those in air medium.The strain energy density ratio of high manganese steel deviated further from 1,and the comprehensive stress corrosion index(I_(SSRT))was also larger,showing higher SCC sensitivity.Moreover,the fracture morphology of all the samples in air exhibited the characteristics of dimple micropore ductile fracture.In solution,the SSRT fracture morphology of 9Ni steel presented typical ductile-brittle mixed fracture characteristics,while that of high manganese steel presented obvious transgranular quasi cleavage brittle fracture characteristics.Besides,the pretensile deformation sample of high manganese steel had higher corrosion current density and more negative corrosion potential.Mn had a strong grain boundary segregation effect,which was easy to cause transgranular SCC.In general,the SCC mechanism of high manganese steel could be attributed to the combined action of hydrogen induced cracking(HIC)and anodic dissolution(AD).