17-7PH沉淀硬化不锈钢安全阀弹簧断裂原因分析

Fracture analysis of 17-7PH precipitate hardened stainless steel safety valve spring

17-7PH沉淀硬化不锈钢安全阀弹簧在服役时断裂。对断裂原因进行分析,结果表明:安全阀弹簧服役环境存在含S、Cl等具有强烈腐蚀性的化学介质,同时失效件断口均发现类似的腐蚀性元素,断口特征与应力腐蚀断裂断口吻合。断裂源区外表面均存在腐蚀磨损,破坏了材料表面完整性尤其是富Cr氧化膜层,加速了环境对弹簧基体的腐蚀,在应力作用下导致应力腐蚀断裂。通过优化系统配合度,避免磨损,隔离腐蚀环境,可以有效防止断裂。

17-7PH precipitate hardened stainless steel safety valve springs were found to be broken in service.The fracture causes were analyzed.Results show that there are chemical media with strong oxidation corrosion such as S and Cl in service environment of safety valve spring,and similar corrosive elements are found on fracture of failed parts,and fracture characteristics are consistent with stress corrosion fracture.There were corrosion wear marks on outer surface of fracture source area,which damaged the surface integrity of material,especially the Cr rich oxide film,accelerated corrosion of the spring substrate,and lead to stress corrosion fracture under action of tensile stress.The failure can be effectively prevented by optimizing system compatibility to avoid wear and isolate the corrosive environment.