航空发动机供油管裂纹失效分析

针对某航空发动机供油管钎焊焊缝边缘出现裂纹而导致的供油管渗油故障,对其断口及源区附近表面进行宏、微观检查,明确了供油管裂纹性质为高周疲劳裂纹,疲劳源区呈沿晶开裂特征。利用能谱分析手段发现裂纹源区存在外来Cu元素,通过对焊缝及开裂部位进行金相分析,发现钎焊料中的Cu元素沿基体晶界发生扩散,导致晶界粗化,在拉应力作用下,Cu与基体形成的脆性相开裂形成沿晶裂纹。晶界粗化和沿晶裂纹是供油管过早发生疲劳开裂的主要原因。建议将Cu基钎料更换为Ag焊料。

Failure Analysis of Fuel Supply Pipe Crack in Aeroengine

In view of the fuel leakage failure of fuel supply pipe caused by crack at the edge of brazing welding of an aeroengine fuel supply pipe,the fracture and the surface near the source region were examined by macro and microcosmic examination.It was clear that the crack property of the fuel supply pipe was a high-cycle fatigue crack,and the fatigue source region was characterized by intregranular crack.The presence of external Cu element in the source of crack was found by means of energy spectrum analysis.Based on the metallographic analysis of the weld and cracking site,it was found that the Cu element in the brazing solder diffused along the matrix grain boundary,which led to the grain boundary coarsening.Under the action of tensile stress,the intergranular cracks was formed by brittle phase cracks formed by Cu and matrix.Grain boundary coarsening and intergranular crack were the main cause of the early fatigue crack of the fuel supply pipe.It is recommended that the Cu-based brazing material be replaced with Ag solder.