表层富立方相功能梯度硬质合金的烧结工艺

Sintering Process of Functionally Graded Cemented Carbides with Cubic Rich Surface

本文对表层富立方相功能梯度硬质合金的三套烧结工艺进行了分析和对比。结果表明:烧结工艺的主要影响因素包括烧结温度、烧结时间及充气方式。在满足梯度层组织结构要求的前提下,应尽量降低烧结温度、缩短烧结时间,以防止晶粒粗化。气体在液相出现后充入,可加快反应速率且有利于消除孔隙。所制备的样品表面均生成了梯度层,其主要成分为富含Ti元素的立方相组织。根据分析结果,笔者对烧结工艺进行了重新设计。在液相温度进行气氛烧结后,控制降温曲线,在固相阶段进行保温烧结,以进一步增加梯度层厚度,同时对梯度层进行均匀化处理,消除内应力。

Three sintering processes of the functionally graded cemented carbides with cubic rich surface were analyzed and compared.The results show that the sintering process are mainly influenced by sintering temperature,sintering time and atmosphere charging mode.Under the precondition of satisfed microstructure and no grain coarsening within the graded layer,the sintering temperature and time should be as low as possible.The atmosphere was built up in the furnace as the liquid phase appeared,which can accelerate the reaction rate and be beneficial to eliminate pores.All the surfaces of samples have formed graded layers,which are all Ti rich cubic phase.Based on the above results,the sintering process was redesigned.After atmosphere sintering at the temperature of liquid phase,isothermal sintering at the temperature of solid phase was held by controlling the cooling curve.The isothermal sintering can further increase the thickness of the graded layer,meanwhile,homogenization treatment can be taken to eliminate inner stress.