The Preparation And Research On The Microstructure,Mechanical Properties Of (Ti,W,Mo)C-Based Cermets

The thesis summarized the researches and developments of Ti(C,N)-based cermetsfirstly and then presented the advantages on strength and toughness of cermets with solidsolution hard phase. Based on these, the objective and meaning of the work were proposed.The carbon thermal reduction method were used to prepared (Ti,W,Mo)C with TiO2,WO3,MoO3and C raw materials.(Ti,W,Mo)C-based cermets were prepared by metallurgytechnology. To test and analyse the carbon thermal reduction product and mechanicalproperties and microstructure of (Ti,W,Mo)C-based cermets, the XRD, OM, SEM, EDS,bending strength tester, Rockwell hardness and Vickers hardness tester were employed.The carbon thermal reduction process was finished and fine (Ti,W,Mo)C solidsolution was synthesized at1300℃for2h for raw powders after high-energy milling for48h.The samples prepared by the mixed powders milled for48h presented the highestcompactness and best mechanical properties: TRS,1500MPa, HRA90; The1450℃wasthe most proper sintering temperature with TRS1751MPa, HRA91.3and KIC14.56MPam1/2; When the addition of Mo was8wt%, the samples got the optimal properties:TRS,1820MPa. HRA didn’t change obviously. The maximum of KICwas15.30MPam1/2with12wt%Mo addition.In the microstructure images, only hard phase and binder phase were observed exceptthe dark holes with or without Mo addition. The size of particles didn’t change obviouslywith the improvement of sintering temperature at the beginning and growed after1450℃;The proper addition of Mo can increase the compactness, however, excessive resulted inthe growth of grains and increased the difficulty of sintering. The analysis to the fracturegraphs indicated that the intergranular brittle fracture was the main fracture way. Above1300℃, some cleavage fracture phenomenon was observed and after adding some Mo,some dimples and tearing ridges existed.