原位研究M2高速钢微裂纹的萌生和扩展

In-situ Study of Microcrack Initiation and Propagation of M2 High Speed Steel

使用扫描电子显微镜(SEM)内的原位加载台对M2高速钢进行了原位拉伸实验。结果表明:在M2高速钢的原位拉伸过程中,微裂纹主要在大尺寸共晶碳化物与基体的界面处萌生和扩展。与回火马氏体相比,裂纹更容易在残余奥氏体上萌生。碳化物的尺寸、形状和种类,对微裂纹的萌生和扩展也有重要的影响。减少块状残余奥氏体、一次共晶碳化物和MC碳化物的数量、减小碳化物的尺寸和改善碳化物形状,可减缓微裂纹的萌生和扩展。

The tensile behavior of M2 high speed steel was studied by using an in-situ loading platform in scanning electron microscope(SEM).The results show that during the in-situ tensile process,microcracks mainly initiate and propagate at the interface between large eutectic carbide and the matrix of M2 high speed steel.Compared with the tempered martensite,cracks initiate more easily on the retained austenite.The size,shape and type of carbides also have important effect on the initiation and propagation of microcracks.It follows that reducing the amount and the size of massive residual austenite,primary eutectic carbides,and MC carbides,as well as appropriately adjusting the shape of carbides can slow down the initiation and propagation of microcracks.