回火马氏体钢锻件蠕变疲劳交互作用研究

Study on creep fatigue interaction of tempered martensitic steel forging

为研究1Cr11Ni2W2MoV回火马氏体不锈钢锻件在高温环境下的蠕变疲劳交互作用行为,加工哑铃状试样在电液压伺服试验机上开展不同峰值应变保持时间的低周疲劳试验。试验后,利用光学显微(OM)和扫描电子显微镜(SEM)对试样断口形貌和纵截面损伤特征进行分析。研究结果表明:随应变保持时间增长,循环软化效应加剧,迟滞回线的非弹性应变范围增大,疲劳寿命降低;断口形貌中疲劳辉纹特征减少,出现明显的韧性损伤特征;纵截面上次级裂纹增加,主裂纹路径在较长应变保持时间下更加曲折。原材料的微空洞缺陷在长保持时间下对主裂纹的扩展产生诱导作用,造成的损伤更大。蠕变疲劳交互作用体现在应变保持加剧循环软化效应和削弱材料抵抗裂纹萌生、扩展能力两个方面。

In order to investigating the creep-fatigue interaction behavior of 1Cr11Ni2W2MoV tempered martensitic stainless steel forging under high temperature environment,dumbbell specimens were machined,and low cycle fatigue tests with different peak strain hold time were carried out on an electro-hydraulic servo testing machine.After test,the fracture morphology and longitudinal section damage characteristics of fatigue specimens were analyzed by optical microscopy(OM)and scanning electron microscopy(SEM).It was found that longer hold time enhanced the cyclic softening effect,which enlarged the inelastic strain range of hysteresis loop,and caused the decrease of fatigue life.The fatigue striations in the fracture morphology were reduced,but ductile damage characteristics appeared.The secondary cracks increased in the longitudinal section,and the main crack path became more tortuous under longer hold time.The micro-void defects of the raw material induced the propagation of the main crack under long hold time,which resulted in greater damage.The creep fatigue interaction was embodied in two aspects.Strain hold not only intensified cyclic softening effect,but also weakened the ability of material to resist crack initiation and growth.