Cr12MoV模具钢冲头失效原因及改进措施

Failure analysis and improvement measures of Cr12MoV steel punching die

疲劳断裂和崩刃是Cr12MoV模具钢冲头在服役过程中的主要失效方式,为此,对失效冲头的硬度、显微组织和失效形貌进行了测试和观察。研究发现马氏体基体中析出的粗大的或者连续分布的碳化物导致了应力集中,进而导致冲头的疲劳性能和断裂韧性下降。对冲头进行调质处理,碳化物明显细化,且弥散分布,提升了冲头的使用寿命,此时冲头的失效方式主要为磨粒磨损。为了进一步提升冲头的寿命,在调质处理后的冲头表面采用真空阴极弧离子镀的方法沉积了AlCrTiSiN涂层。与调质处理的冲头相比,沉积AlCrTiSiN涂层冲头的寿命延长了50%左右,这主要是因为AlCrTiSiN涂层具有高的硬度和低的摩擦因数。

Fatigue fracture or local collapse in edge were the main early failures of Cr12MoV steel punching dies during service.Microstructure,fracture morphologies and hardness of the failed punch were investigated. The results show that the numerous coarse carbides and carbides line precipitated in martensitic matrix result in stress concentration,and further deteriorate the fatigue performance and fracture toughness. After quenching and tempering,the coarse carbides are notably refined and well dispersed. As a result,the service life of the quenched and tempered dies is considerably improved,due to the main failure mechanism becoming abrasive wear. Furthermore,AlCrTiSiN coating was deposited on the quenched and tempered dies by cathodic vacuum arc,and the service life of the coated dies was enhanced about 50% when compared with that of the quenched and tempered one. Therefore,the improvement of service life is attributed to higher hardness and lower friction coefficient of the coating.