Effect Of Binder And Addition(C,W) On The Microstructure And Mechanical Properties Of Ti(C,N)-based Cermets

The origin, course of developing, performance character, condition of using and chance for developing these days of Ti(C,N)-based cermets are introduced in this paper. The raw components and microstructural features of Ti(C,N)-based cermets are described, especially the effects of C, WC and Mo on the properties of this material. The importance of the planetary milling to the Ti(C,N)-based cermets are summarized. Binders used for die pressing are introduced, especially SBS binders used widely in manufacturing hard-metals.In the study of the effect of the distributing of the ball diameters on mechanical properties and microstructure of Ti(C,N)-based cermets, it is found hat the diameters of the long used balls are always not equality, the grain size of the powders milled by this kind balls is bigger and not uniform. The result shows: microstructure is course, crystal grains are not homogeneous, and mechanical properties are poor. Ethanol is not the best milling medium, because Mo in the milled powders is oxidized, existed in Ce(MoO₄)₂. The prevention of oxygenation of hexane and hexane & wax are better than ethanol.The processing of die pressing for Ti(C,N)-based cermets is important too. In this paper binders of wax, PVA, sodium rubber and SBS are analyzed. The process of dewaxing of SBS is slower than others, and the remainder C is very little. Those characters of SBS are beneficial to the larger products and controlling the mechanical performances. The density and performances of the samples used SBS as binder is higher than which used others. The preferable quantity of SBS is 40ml/kg.Addition of C is important to the properties of Ti(C,N)-based cermets. If there is too little C,ηphase will be found in the microstructure, and if there is too much C, dissociative C will appear in the mircostructure. Those two phases are no good for improving mechanical performance of Ti(C,N)-based cermets. In this test, the best addition of C is 0.9wt%, the TRS is higher than any others, although the hardness is a little lower. When graphite and diamond are added at the same time, mechanical performance is not improved. The TRS and hardness of this kind sample is as low as the same quantity graphite sample. That demonstrates the atoms of C leave away the regular tetrahedron structure of diamond, and reaction with other elements.When Mo is replaced by W, Ti(C,N)-based cermets can be sintered perfectly. The TRS is higher than common Ti(C,N)-based cermets contain Mo, but the hardness is a little lower than common cermets. The graph of the TRS changed with sintering temperature is a"W"shape, the complicated change may be controlled by dimension of crystal grain and wettability of the ceramic and metal phases. A classical core-rim microstructure of Ti(C,N)-based cermets is observed in this Mo-free material too. The outer rim is quite thick, and the inner rim is very thin. The inner rim is rich-W (W,Ti)(C,N) phase, and the outer rim is rich-Ti (Ti,W)(C,N) solid solution. There is much W in the binder phase, existed in Ni17W3 and strengthen that.