Study On Microstructure And Properties Of TiCN Reinforced Iron Matrix Composites

Compared with WC-Co cemented carbide,steel bonded cemented carbide has excellent machinability,heat treatment,high strength and toughness.TiCN has high melting point,high hardness,excellent corrosion resistance and oxidation resistance.However,TiCN is a single compound formed by continuous solid solution of TiC and TiN.The wettability between TiN and Fe is poor,and the interfacial adhesion is weak,which leads to the decrease of strength and toughness of the alloy.In order to solve the problems of insufficient strength and toughness,wear resistance,corrosion resistance,temperature resistance and machinability of TiCN based steel bonded cemented carbide,conventional cobalt bearing powder metallurgy high speed steel(ASP30,6W-5Mo-4Cr-3V-8Co)and a new type of non carbon age hardening steel(Fe-25Co-15Mo)were used to prepare TiCN based steel bonded cemented carbide.The effects of heat treatment process on the microstructure and properties of the composites and their respective strengthening mechanisms are discussed.The effects of milling time and sintering temperature on the microstructure,densification mechanism and mechanical properties of the materials were studied,and the optimal preparation process was established.The relevant conclusions of TiCN based high temperature steel bonded carbide and TiCN strengthened powder metallurgy high speed steel ASP30 are as follows:(1)In the process of preparation and forming of TiCN based high temperature steel bonded cemented carbide,the best milling time of the material is 32h and the best sintering temperature is 1425?.The size fluctuation of hard phase is stable and uniform under the micro morphology.The density is 6.92g/cm~3,the hardness and transverse fracture strength are 62.60HRC and 1376.64N/mm2 respectively.(2)During the research of the heat treatment process of TiCN based high temperature steel bonded cemented carbide,the properties of the materials have not changed and improved with the change of quenching temperature,but the subsequent hot isostatic pressure process has a more obvious influence on the transverse fracture strength and the hardness of the material.The transverse fracture strength of the material after hot isostatic pressure treatment is 2224.26N/mm~2,and its performance is increased by 41%;the hardness of the material is reduced by about 5HRC in quenching state after quenching after tempering treatment,and the hardness after tempering treatment will have the property of 11HRC.(3)In the tempering treatment of TiCN based high temperature steel bonded cemented carbide,the hardness of the material reaches the highest at 520?,73.1HRC,and still shows higher hardness in the subsequent tempering temperature,and 65.8hrc at 700?.The maximum values of impact toughness and transverse fracture strength of the materials are 4.70J/cm~2and 2227.35N/mm~2when tempered at 700?.Moreover,the material can obtain higher tempering hardness in a very short time(5 min),and there is no significant decrease trend with the extension of tempering time.(4)During the research of the spinning forging process of TiCN reinforced ASP30 powder metallurgy high speed steel,the deformation of swaging is 0%,21%,40%,56%and 73%.The results show that the wear resistance of ASP30 high speed steel can be improved and the wear profile can be improved by adding TiCN.The bending strength and impact toughness of the high speed steel reinforced by TiCN can be improved significantly when the deformation of spinning forging is 56%.The best performance is 14.55J/cm~2and 4084.99N/mm~2.