WC-Ti(C, N)-Co梯度硬质合金表面韧性区的形成机理

从动力学的角度分析WC—Ti（C，N）-Co硬质合金在液相烧结过程中表面韧性区的形成机理。借助金相显微镜、扫描电镜、能谱仪、X射线衍射仪和切削实验研究表面韧性区梯度硬质合金的微观结构和性能。研究结果表明：由于N原子与Ti原子之间强烈的热力学耦合作用，N原子和Ti原子在液相烧结过程中朝相反的方向迁移，在合金表面形成缺立方相碳化物的韧性区；与合金内部的WC晶粒相比，韧性区内WC晶粒度更细，晶体取向发生改变；刃口附近前、后刀面的表面韧性区的厚度呈现梯度变化；在合金内部存在环形相结构的立方碳化物；表面韧性区使合金的强度提高，使涂层刀片的抗冲击性能提高1.6倍。

Formation mechanism of surface ductile zones in WC-Ti(C, N)-Co gradient cemented carbide

The formation mechanism of surface ductile zone during liquid sintering of WC-Ti(C,N)-Co cemented carbides was studied from thermodynamics angle.The microstructure and property of surface ductile zones were investigated with optical microscopy, scanning electron microscopy,energy dispersive X-ray spectroscopy,X-ray diffraction strength measurements and cutting tests.Due to strong thermodynamical coupling between N and Ti,the outward diffusion of N during liquid sintering of WC-Ti(C,N)-Co cemented carbides leads to an inward diffusion of Ti,and a surface ductile zone deleted in cubic carbides is formed.Compared with WC crystal grain inside the gradient cemented carbide,WC crystal grain in surface ductile zone is smaller and the grain orientation is changed.The gradient alteration occurs to be thickness of rake and flank face near the cutting edge.The core-rim structure of cubic carbides is found.The ductile zone prevents cracks propagation and leads to the increase of the transverse rupture strength.The impact resistance of coated gradient inserts is increased by 1.6 times.