某涡轮后机匣裂纹失效机理分析

为排除某航空发动机斜支板涡轮后机匣在试车后出现裂纹的故障,进行了裂纹宏观检查、断口宏观和微观形貌分析、材质检查、细晶层成因及其对疲劳特性影响分析,并对裂纹性质进行了判定,分析了产生裂纹故障的原因。结果表明:斜支板涡轮后机匣裂纹为疲劳性质,原始铸造冷隔缺陷、热等静压工艺产生的细小再结晶层、基体晶粒粗大是促使涡轮后机匣过早疲劳开裂的主要原因。为避免该类故障再次发生,建议提高浇注温度以增强浇注液流动性,从而排除冷隔缺陷;防止热等静压时产生表面细小再结晶;添加细化剂使基体晶粒细化。

Study on the Crack Failure Mechanism of a Turbine Rear Casing

In order to eliminate the crack fault on the turbine rear casing with tilted-plat,the macroscopic crack and material quality were inspected,the macroscopic and microscopic morphology fracture were analyszed,the origin of fine crystal layer and its influence on fatigue characteristics were analyzed. The crack characteristic was judged and the reason of crack fault was analyzed. The results show that the crack on the turbine rear casing with tilted-plat is fatigue crack,the original casting cold barrier defect,the fine recrystallization layer produced by hot isostatic pressing process,and the coarse matrix grain are the main causes of premature fatigue cracking of turbine rear casing. It is suggested that the pouring temperature should be raised to enhance the fluidity of the casting solution so as to eliminate the cold barrier defect,to prevent the formation of fine recrystallization on the surface during hot isostatic pressing,and to add refiners to refine the matrix grains.