0Cr12Mn5Ni4Mo3Al不锈钢自锁螺母的开裂原因

Crack Analysis of Self-Locking Nut of 0Cr12Mn5Ni4Mo3Al Stainless Steel

某0Cr12Mn5Ni4Mo3Al不锈钢自锁螺母在服役过程中出现开裂。对开裂螺母进行了宏观和微观断口形貌观察、表面能谱分析、显微组织及力学性能分析与测试等。结果表明:该螺母开裂原因为应力腐蚀开裂(SCC)。裂纹起源于法兰面与螺母体交接处,螺母体与法兰面呈直角此处易积液,螺母表面处理方式为钝化和涂MoS_(2),其耐蚀能较差。在腐蚀性潮湿大气环境中,干湿交替作用下螺母产生局部腐蚀点,在腐蚀点处萌生裂纹,裂纹在螺母圆周切向拉应力作用下扩展直至螺母开裂。

A self-locking nut of 0Cr12Mn5Ni4Mo3Al stainless steel cracked during service.Macro and micro fracture morphology observation,surface energy spectrum analysis,microstructure and mechanical properties analysis and testing were conducted on cracked nuts.The results indicate that the cause of the nut cracking was stress corrosion cracking(SCC).The crack originated at the junction between the flange surface and the nut body,where the nut body was at a right angle to the flange surface and was prone to liquid accumulation.The surface treatment of the nut was passivation and MoS_(2) coating,its corrosion resistance was poor.In a corrosive and humid atmospheric environment,localized corrosion points were generated under the alternating action of dry and wet conditions.Cracks initiated at the corrosion points and propagated under the tangential tensile stress of the nut circumference until cracking occurred.