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

Ti(C,N)-based cermets with different compositions were made by powder metallurgical method.The effect of different ZrC content and boronizing on the microstructure and properties of Ti(C,N)-based cermets were studied.The thesis is composed of six chapters.In the first chapter,the development history and application of cermets as well as its microstructure,properties and preparation techniques were introduced.Meanwhile,the category and cutting properties of Ti(C,N)-based cermets cutters were also briefed.In chapter two,experimental raw materials and preparation techniques of TiC/Ti(C,N)-based cermets were introduced simply.In chapter three,the testing methods of mechanical properties and microstructure were focused on.In chapter four,the composition-microstructure-property relationship of TiC-based cermets was discussed,and the effect of different ZrC content on the microstructure and mechanical properties of cermets was reviewed.The conclusion of this study can be summarized as follows:(1)When ZrC was added into cermets, solid solutions of(Ti,Zr)C that were rich of Ti formed and made the grains thicker, and then,with the further addition of ZrC,solid solutions of(Zr,Ti)C that were rich of Zr formed and made the grains thinner.Those structrures were helpful to improve the strength and toughness of the material.What's more,there was classical black core/grey rim structure in the microstructure.(2)A new type white core/grey rim structure and white grians appeared in cermets after the addition of ZrC,which had been regarded as beneficial for the properties of the cermets.(3) ZrC content had little effect on the fracture modes.The typical fracture modes Were intergranular and transgranular fracture.The fracture toughness reached the highest value when ZrC was 30 wt%.(4)Within a certain range,the microstructure became finer with the increasing of ZrC powder addition,which was favorable to the mechanical properties,but the bending strength and hardness decreased due to the decreasing of relative density of the cermets.In chapter five,boronizing treatment was operated on the surface of nano modified Ti(C,N)-based cermets and the cutting performances of cutters before/after boronizing against AISI 1045 carbon steel were researched.The experimental results showed that a series of borides were presented on the surface of cermets and the microhardness of surface increased significantly.Furthermore, the cutting performances of Ti(C,N)-based cermet cutters were compared before and after boronizing at the various cutting speeds.The results showed that the tool life of boronized Ti(C,N)-based cermet cutters exhibited the longer tool life than those without boronizing at lower speed.Granule abrasion,adhesive abrasion, diffusion abrasion and oxidation abrasion were the main wear mechanisms for the Ti(C,N)-based cermet cutters,and there was not only one but multiple wear mechanisms for each cutter.Chapter six summarized the whole thesis and gave some advice on future works.