1Cr18Ni9Ti不锈钢供油管裂纹故障分析

Crack failure analysis of 1Cr18Ni9Ti stainless steel fuel supply pipeline

某类型发动机在进行可靠性测试时,其中一件材料为1Cr18Ni9Ti的供油管出现漏油现象。经过X光探伤检查发现,在供油管扩口R角位置存在一条裂纹。通过对供油管裂纹进行外观检查、金相检查、断口分析检查、化学成分检测及零件在发动机测试过程的情况分析,确定了该R角位置裂纹的性质及产生原因。试验结果表明:供油管上的裂纹性质为疲劳裂纹,疲劳裂纹起源于零件的外表面,呈点源特征,疲劳裂纹的起始应力和扩展应力也相对较小;疲劳裂纹萌生的主要原因,与发动机测试时螺母松动导致的异常振动及源区存在打磨痕迹有关。建议类似供油管零件不再使用砂轮打磨,需要在供油管附件安装卡箍支撑给予固定,防止后续螺母松动再次发生异常振动。

During the reliability test of a certain type of engine,one of the fuel supply pipelines made of 1Cr18Ni9Ti experienced fuel leakage.After X-ray inspection,it was found that there was a crack at the flaring R angle of the fuel supply pipeline.Through appearance inspection,metallographic inspection,fracture analysis and chemical composition detection of the crack of the pipeline,the properties and causes of the R angle crack were determined.The experimental results showed that the nature of the crack was fatigue crack,which originated from the outer surface of the part and exhibited point source characteristics.The initial stress and propagation stress of the fatigue crack were relatively small.The main reason for the generation of the fatigue crack was related to the abnormal vibration caused by loose nuts during engine testing and the presence of grinding marks in the source area.It is recommended that similar pipeline parts no longer be polished with grinding wheels.Instead,clamps should be installed to support and secure the fuel supply pipeline to prevent the loosening of the nuts and the occurrence of abnormal vibration.