加外极化对40CrNi2Si2MoVA钢腐蚀断裂特性的影响

 应用微机辅助电化学测试方法、控制电位慢拉伸及断裂力学试验方法,研究了外加极化对40CrNi2Si2MoVA钢在3.5％NaCl溶液中腐蚀断裂特性的影响。在阳极极化(-635mV)和阴极极化(1 350mV)电位下,慢拉伸断裂总应变ε_f相应为空气中的54％和49％。阳极极化(偶铜)增加了裂纹扩展速率,阴极极化降低了裂纹扩展速度。根据不同条件下腐蚀断裂特性参数的变化,结合宏观及扫描电镜断口分析,该钢在3.5％NaCl溶液中的腐蚀断裂机理为裂尖阳极溶解与氢脆共同作用。

THE EFFECT OF APPLIED POTENTIAL ON CORROSION CRACKING OF 40CrNi2Si2MoVA STEEL

The effect of applied potential on corrosion cracking of 40CrNi2Si2MoVA steel in 3.5% NaCl solution is investigated by using computer assited electrochemical measuring technique, slow strain rate tension and fracture mechanics methods. It has been found that the susceptibility to corrosion cracking of 40CrNi2Si2MoVA steel increases with applied potential. The total elongation to fracture εf of the steel, at-635m V and-1 350mV, is decreased to 54% and 49% of that in air respectively. The (da/ dt) II of the steel increases at anodic polarization (coupling Cu) and decreases at cathodic polarization. According to the variation of corrosion cracking feature in different conditions and SEM fractographic analysis, it is suggested that the corrosion cracking of 40CrNi2Si2MoVA steel should result from the combined action of local anodic dissolution at the crack tip and hydrogen embrittlement.