Research On The Preparation And Mechanical Properties Of Ti(C, N)-based Cermets With Double Structure

Ti (C, N)-based cermets have been widely concerned、researched and useddue to its excellent mechanical and physical properties since Ti (C,N)-basedcermets are produced in1929. In this paper，the Ti(C,N)-based cermets withconventional structure (named conventional cermets) were synthesized bypowder metallurgy process. After manually crushed and sieved, three groups ofgranules which have different particle size were obtained, then mixed the threegroups of granules with Ni, Mo binder phase that pre-mixed homogeneousrespectively and milling a little time, Then dried, granulation and pressing.Finally, sintered the sample at1400°C (0.1Pa) for an hour in vacuum furnaceand the Ti(C,N)-based cermets with double structure (named double cermets)were prepared. The cermets were analyzed by means of XRD、SEM and EDX.Effect of different granules size on the microstructure and mechanical propertiesof double cermets was studied.This thesis is divided into five chapters, the first chapter of the paper gives adescription about the history,development, class，the preparative techniques ofcermets and the development status of double cermets, and also illustrated thepurpose and meaning of our research.The chapter two introduces the experiment design of the conventional Ti(C,N)-based cermets and double cermets.In chapter three, the preparation of conventional Ti(C, N)-based cermets andgranules（after crushed the sintered samples）which have been used in next, thepreparation of double cermets as well as characterization techniques ofmicrostructure and mechanical properties are introduced.In chapter four, the microstructure and mechanical properties of conventionalTi(C, N)-based cermets and the effect of different granule size on themicrostructure and mechanical properties of double cermets was studied, and thegranule size-microstructure-mechanical property of double cermets werediscussed. The results show that：（1）The microstructure of double cermets is aspecial organization, which manifest a large number of granules embedded inthe binder phase matrix, the microstructure (BSE mode) of granules inside is thetypical dark core-grayish rim structure, and a small amount of white core andgrayish rim structure is also observed.（2）The double cermets, due to the granules distributed in the binder phase matrix play a leading role in TRS. TheTRS of double cermets, based on Hall-Petch formula and considering all factors,is less than conventional cermets, and decreases with the increase of granulesize. The hardness of double cermets is less than conventional cermets, and alsodecreases with the increase of granule size.（3）Both the granules and binderphase matrix lead to mean free path increases in double cermets. In addition, thecrack deflection, branching and bridging of granules internal which make it canabsorb more energy before breaking, and make it has much improvement infracture toughness. What’s more, the fracture toughness increased with theincrease of granule size.Finally, the chapter five made a brief summary of the full text and put forwardsome suggestions for future works.