本文研究了40CrNi2Si2MoVA超高强度钢在两种热处理状态(油淬和270℃等温淬火)下,显微组织与其冲击疲劳裂纹起始寿命之间的关系,探讨了超载对冲击疲劳裂纹起始寿命的影响.结果表明,裂纹起始是马氏体或贝氏体板条间相对滑动形成微裂纹,继而连接、长大的过程;减少残余奥氏体量,提高屈服强度,可使冲击疲劳裂纹起始寿命增长;在一定条件下,超载可显著延长冲击疲劳起始寿命.
Abstract
In the present paper,the influence of microstructure on impact fatigue crack initiation life(FCIL)of 40CrNi2Si2MoVA ultrahigh strength steel was investigated.Two kinds of microstructure were adopted by oil quenching and isothermally quenching at 270℃.And overload effect on FCIL was studied.The results show that,the relative sliding of martensite or bainite laths leads to the micro-crack initiating and growing up to a macro-crack.With decreasing retained austenite amount and increasing yield stress,the FCIL will be enhanced.In a certain condition,overload can markedly prolong FCIL.
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