硅对烧结M3∶2高速钢回火相及力学性能的影响

为研究硅对烧结高速钢力学性能的影响,采用真空热处理炉在1230℃对含0.4%碳粉及硅添加量在0～3.0%的M3∶2高速钢进行烧结,在500～600℃对烧结后的试样进行二次回火.采用X射线衍射仪,扫描电镜及能谱分析等手段研究了不同硅添加量对回火态高速钢的物相特征及力学性能的影响规律.物相分析结果表明,添加硅后,硅主要分布在回火马氏体及M6C碳化物中,而在MC碳化物中含量较低.回火马氏体组织中硅的含量随硅添加量的增加而增加,同时,硅的添加还显著影响回火马氏体组织中铁素体相的晶格常数,在硅添加量为0.7%时,铁素体相达到最大的晶格常数.力学性能测试结果表明,适量硅的添加可提高二次硬化效果,添加0.7%硅的高速钢在550℃二次回火后获得了最佳的硬度和弯曲强度.

Effects of silicon addition on tempering phase and mechanical properties of sintered M3∶2 high-speed steel

To investigate the improvement of mechanical properties of high-speed steel by silicon addition,M3∶2 high-speed steel with carbon addition of 0.4 wt.% and silicon addition in the range of 0~3.0 wt.% was sintered at 1230 ℃ using vacuum heat treatment furnace,and then followed by double tempering between 500 ℃ and 600 ℃.Effects of silicon addition on phase characteristics and mechanical properties of tempered M3∶2 high-speed steel were investigated by using X-ray diffraction,scanning electron microscopy,and energy spectrum analysis. Phase analysis results show that silicon distributes mainly in tempered martensite and M6C carbides,but rarely in MC carbides. The content of silicon in tempered martensite of high-speed steel increases with the increasing silicon addition. The addition of silicon exerts a crucial role on the the lattice constant of ferrite in tempered martensite. For the case of 0.7 wt.% silicon addition,the alloy exhibits the maximum lattice constant. Mechanical property test results show that suitable silicon addition can improve the secondary hardening effects of M3∶2 high-speed steel. M3∶2 high-speed steel with 0.7 wt.% silicon addition possesses the excellent combination of high hardness and high bending strength after double tempering at 550 ℃.