Effect Of Powder Size On Microstructure And Properties Of Ti(C, N)-based Cermets

As we know, grain refinement is an effective method to improve the strength and toughness of the alloy material. From this view, we have researched the influence of powder size on the microstructure and mechanical properties of Ti(C,N)-based cermets on the condition of identical component and fixed preparation technology, and have found the relationship of initial powder size and the microstructure and mechanical properties.Firstly, we briefly introduced the development history, the questions and difficulty in the present study and the future trend of Ti(C,N)-based cermets. At the same time, several present researching emphasis were reviewed, such as: the study on the phase interface between hard phase and binder, the effectiveness of addition agents and powder size on the microstructure and mechanical properties.Secondly, In chapter three ,we pointed out that the homogeneous degree of powder mixture, the choice of pressure force in pressing and the control of the technology in sintering were the key steps to determine the microstructure and properties of cermets in the preparation process. In chapter four, we simply instructed the equipment needed by testing method of main mechanical properties parameters of Ti(C,N)-based cermets,Finally, we analyzed the effectiveness of initial powder size on the microstructure and properties of cermets in chapter five. And we pointed out the future emphasis in this aspect in chapter six. Results show that:(1) Though powder size changed, no new phase formed. With the refinement of the powder size, the amount of solid solution element in Ni/Co binder and the side-play amount of XRD diffraction peak increased.(2) There are many black-core and gray-rim phases in microstructure. With the refinement of the initial powder size of TiC/TiN, the grain size of hard phase become fine, and white-core phase become more. By EDS energy spectrum analyzing, we know that the black-core phase is mostly made up of TiC/ Ti(C,N),gray rim is (Ti,W,Mo)(C,N),the white rim is Ni/Co binder which contains more W and Mo elements and the white-core phase mostly is WC or (W,Mo)(C,N) solid solution;Besides, we also found few white-inner rim in the microstructure.(3) With the refinement of the initial powder size of TiC/TiN, the binding strength increases and changes more, the fracture toughness reduces, and thehardness varies little. The cause is as follows: (a)In the cermets made from the fine powders, the amount of solid solution element in Ni/Co binder is greater, so toughness reduces;(b) the surface energy of fine grain is greater and the raw material contains too more oxygen or other contaminates which reduces the wettability between binder and hard phase, the bond strength of phase interface is weakened, so the fracture toughness of cermets reduces.(4) The future emphasis of investigation on Ti(C,N)-based cermets should focus on the research of the phase interface between hard phase and binder,...