17-4PH推靠头断裂失效分析

Fracture Failure Analysis of 17-4PH Pusher

某井壁取心仪器推靠器结构中推靠头与螺钉发生断裂。通过对断裂件断口进行宏观与微观分析,确定推靠头的失效模式为解理断裂、螺钉的失效模式为疲劳断裂。两者的化学成分符合标准对于17-4PH钢的技术要求,推靠头的硬度值符合标准要求,螺钉的硬度值低于标准要求下限。金相组织分析结果显示,除正常的马氏体组织外,两者均含有δ-铁素体的存在。综合理化试验结果与推靠器结构特点,判定出螺钉为首断件。

The sidewall contact device of CMRT was broken:the pusher head and the screw broken.Through the macro and micro analysis of the fracture surface,it is determined that the failure mode of the push head is cleavage fracture,and that of the screw is fatigue fracture.The chemical compositions of the two cracked parts meet the technical requirements of 17-4PH.The hardness value of the pusher head meets the standard requirements,and the hardness value of the screw is lower than the standard requirements.The results of metallographic structure analysis show that both containδ-ferrite except normal martensite.Based on the physical and chemical test results and the structural characteristics of the thruster,the screw is determined to be the initial fragment.