研究了Ｗ１８Ｃｒ４Ｖ高速钢激光相变强化层的组织及奥氏体晶粒超细化的机理．强化层的组织由马氏体、残余奥氏体及未溶碳化物组成，其中片状马氏体量较多，板条马氏体量较少，其亚结构分别为孪晶和密度较高的位错．残余奥氏体量约为１０％～１５％，较常规热处理有明显减少，激光相变强化后晶粒度由原来的８级提高到１２级． The microstructure and austenite grain refinement mechanism of laser phase transformation strengthened layer of W18Cr4V high speed steel was studied. The microstructure of the strengthening layer consists of martensite, retained austenite and undissolved carbides. Among them, the amount of lamellar martensite is larger and the amount of lath martensite is smaller, and the substructures are twins and higher densities respectively Dislocation. The amount of retained austenite is about 10% ~ 15%, which is obviously lower than conventional heat treatment. The grain size after laser phase transformation strengthening is increased from 8 to 12.