Effect Of Carbon Content On The Microstructure And Properties Of Ti(C, N)-based Cermets

As a new kind of tool materials which appeared in the seventies, the Ti(CN) based cermets have been widely used in recent years due to many of its good properties. We prepared the samples that had different carbon content by the method of powder metallurgy and explained macro mechanical properties of this material by means of XRD, SEM, EDX and so on.This thesis is composed of five chapters. In the first chapter, the microstructure, properties of Ti(CN) based cermets as well as its development history and application in metal cutting area were introduced. Based on above work, the purposes and significance of this thesis have also been pointed out. Meanwhile, the development trend of nanocomposite ceramics was also briefed.In chapter two, experiment raw materials and preparation techniques of ultra-fine grade Ti (CN)-based cermets were introduced briefly. In chapter three, we focused on the testing method of mechanical properties and token method of microstructure of ultra-fine grade Ti (CN)-based cermets.In chapter four, we discussed the composition-microstructure-property relationship of ultra-fine grade Ti (CN)-based cermets, and we reviewed the effect of different carbon content on the microstructure and mechanical properties of cermets. Results show that: 1) within a certain range, the microstructure become fine with the increasing of carbon powder addition and the solubility of the elements of Mo, W, Ti in the binder phase reduce. The fine grains helped to improve the strength and hardness of the material.2) A new type white core/grayish rim structure appeared in cermets fabricated from sub-micron sized Ti (CN) starting powders. It was believed that promoted diffusional reaction caused by ultra-fine raw powders led to the formation of this new core/rim structure which helps to improve the strength and toughness of the material.3) If the addition of carbon contents is too little or too much, the phase composition of material will deviate from the normal dual phase section and lead to the formation of the third phase: η phase or dissociative carbon. And the formation of the third phase will remarkably deteriorate the mechanical properties of cermets.Chapter five summarized the whole thesis and gave some advice on future works.