高温退火和添加Si对仿M10铁基烧结合金显微组织的影响

在一种仿M10粉末冶金铁基烧结合金显微组织中出现了针状碳化物,通过高温退火和添加Si元素的方式研究了针状碳化物的演变特征.采用X射线衍射和能谱分析确认了这是一种M2C型碳化物.结果表明：M2C是一种稳定性较高的亚稳相,高温退火时Mo、Cr、V元素向基体内扩散使M2C可以断裂、球化和分解.提高退火温度能加快针状碳化物形貌和结构的转变.Si元素可进入更稳定的M6C型碳化物中,抑制M2C的形成,显微组织中针状和块状碳化物共存.

Effects of annealing and adding Si on the microstructure of M10 type sintered steel

A kind of needle shaped carbide presents in the M10 type sintered steel. The microstructure evolution was investigated by means of annealing at high temperature and adding Si. The needle shaped carbide was verified to be M2C carbide by XRD,metallurgical and EDS techniques. The characteristic of its composition was that Mo, V content was relatively high and Fe content was low. The results show that M2C has high stability, but can fracture, spheroidize and decompose during annealing. At the same time, the changes in metallurgical morphology and chemical composition of the carbide result from the diffusion of Mo, Cr, V out of the carbide into the matrix, which can be strengthened by the increment of annealing temperature. The needle shaped carbide can be hindered by the addition of 1wt% Si since it is beneficial to the formation of M6C carbide, so that the needle shaped carbide and block carbide coexist.