无η相梯度WC-Co硬质合金的微观结构与性能

Microstructure and Properties of Functionally Gradient WC-Co Hardmetals without η Phase

采用气氛烧结法制备了无η相梯度WC-Co硬质合金,并通过扫描电子显微镜观察渗碳处理前后样品的微观形貌和WC晶粒尺寸,X射线能谱仪测量Co含量的分布,X射线衍射仪分析样品的相结构,显微硬度计测量样品表面、心部的硬度,X射线应力仪测量样品烧结表面的残余应力,钴磁测量仪和矫顽磁力计测量样品的钴磁值、矫顽磁力,对梯度硬质合金的微观结构和性能进行了分析。结果表明,通过渗碳处理可以制备出无η相的梯度WC-Co硬质合金,WC晶粒有长大的趋势,但长大幅度较小;渗碳处理后合金钴磁值增大,矫顽磁力减小;梯度硬质合金的硬度呈梯度分布,表面硬度显著高于渗碳处理前的硬质合金的平均硬度;梯度硬质合金烧结表面的残余应力为压应力,残余应力数值低于渗碳处理前的硬质合金。

Functionally gradient WC-Co hardmetals without η phase were fabricated via controlled atmosphere sintering method. The microstructure and WC grain size of the hardmetals before and after carburization were observed by scanning electron microscope （SEM）. The cobalt content distribution and the phase structure of the hardmetals were determined by energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）, respectively. The hardness on the surface and in the core of the hardmetals was determined by micro hardness tester. The residual stress on the surface of the hardmetals was determined by X-ray stress analyzer. The cobalt magnetism and coercive force of the hardmetals was determined by cobalt magnetism tester and coercive force meter, respectively. The results show that functionally gradient WC-Co hardmetals without η phase can be fabricated via carburization treatment. The WC grains grow up in a narrow range. After carburization, the cobalt magnetism of the gradient hardmetals increases whereas the coercive force decreases, The hardness of the hardmetals shows gradient distribution, and the surface hardness is higher than that of the hardrmetals before carburization. The residual stress on the surface of the gradient hardmetals is compressive stress, its value is lower than that of the hardrmetals before carburization.