某飞机在进行检查时发现,其起动机GH1140高温合金排气导管内层加强筋处有一条裂纹, 采用化学成分分析、金相检验、断口分析等方法对裂纹产生的原因进行了分析。结果表明: 由于高温气体的冲刷作用使排气导管内表层晶界出现了贫铬, 降低了合金的强度、持久性能和疲劳性能; 排气导管开裂主要是由于其内表面曾被打磨, 打磨处形成应力集中萌生裂纹源, 在起动机内部反复热应力和机械振动等作用下, 以及表面氧化物的进一步促进作用下发生的热疲劳开裂。

A crack was found in the inter stiffener of GH4110 high temperature alloy vent-pipe of starting engine when the plane was checked. Chemical compositions analysis, metallographic examination and fracture analysis were used to analyze the cracking reason of the vent-pipe. The results show that the grain boundary presented poor chromium in the pipe inwall surface because of the role of high-temperature gas erosion, which reduce the strength, lasting and fatigue properties of the alloy. The vent-pipe failure was the thermal fatigue cracking, which was caused by the stress concentration of the ground place, interior heat-stress and mechanical vibration.