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通过透射电子显微镜分析研究了W4Mo3Cr4VSiN(F2 0 5 )低合金高速钢在 116 0℃淬火 ,2 5 0～ 70 0℃不同温度下回火时马氏体二次硬化的原因、碳化物析出机理。结果表明 :在回火温度为 35 0℃时 ,F2 0 5钢从基体中析出大量的Fe3 C ;5 2 0℃时Fe3 C消失、重溶 ;5 4 0℃时有类似于Al Cu合金中的GP区的W、Mo等合金元素与碳原子组成的复合偏聚区存在 ;5 6 0℃时 ,有面心立方的Mo2 C和Cr7C3 从基体中弥散析出 ,与此同时W、Mo等合金元素与碳原子组成的复合偏聚区逐渐减少 ,使得F2 0 5钢二次硬化效应达到了最大值 ;在 70 0℃左右 ,Mo2 C晶格发生变化 (Mo2 C(fcc)Mo2 C(hcp) )。
The causes of secondary hardening of martensite and the precipitation mechanism of carbides during the tempering of W4Mo3Cr4VSiN (F2 0 5) low alloyed high speed steel at 116 ℃ and tempering temperatures from 250 ℃ to 70 ℃ were studied by transmission electron microscopy. The results show that a large amount of Fe3C is precipitated from the matrix when the tempering temperature is 35 0 ℃, Fe 3 C disappears and re-dissolves at 520 ℃, Of the GP region W, Mo and other alloy elements and carbon atoms of the composition of the segregation zone exists; 5 6 0 ℃, the face-centered cubic Mo2 C and Cr7C3 dispersed from the matrix, at the same time W, Mo and other alloys The segregation of elements and carbon atoms in the composite segregation zone decreased gradually, which made the secondary hardening effect of F2 05 reach the maximum value. At 70 0 ℃, the lattice of Mo2 C changed (Mo2 C (fcc) Mo2 C (hcp )).