直升机旋翼桨根衬套热处理后硬度降低的原因

Hardness Decreasing Reason of Airscrew Bush Parts of Helicopter after Heat Treatment

直升机旋翼桨根衬套在热处理后硬度低于设计规范要求。通过显微组织观察和微区成分分析以及对加工过程进行检查,认为衬套在固溶处理过程中造成了表层增碳,使表层组织中的马氏体量减少,残余奥氏体量增加,导致硬度降低;又由于没进行后续精加工,增碳层没去除掉,造成产品表面硬度达不到设计要求。

The hardness of airscrew bush parts of helicopter after heat treatment was lower than the required value of design specification. The results of microstructure observation, composition analysis and process checking- up indicated that the essential reason of hardness decreasing the parts was as follows. The surface layer carbureting during the solid solution and aging process resulted in the decrease of martensite and increase of retained austenite in the surface layer mierostructure and thus led to the reduction of hardness. In addition finish machining was not preformed to remove the surface carbureting layer so that the hardness was lower than the design specification.