Study On Preparation And Heat Treatment Of Ti(C,N)Based Steel Bonded Carbide

The most commonly used material in the cutting tool industry in the last years has been the cemented carbide?WC-Co?.However,there is an interest to look for alternative materials due to its high cost and toxicity.Ti CN based cermets could be a competitive option due to their good properties such as hardness,wear and oxidation resistance,nevertheless the metals which are conventionally used as metallic matrix are Ni and Co,which show the same problems of cost and toxicity as cemented carbide.In this work the use of Fe as alternative metallic matrix is proposed.The advantage in the use of Fe is its high cost-effective,low toxicity and heat treatable.The disadvantage in the use of Fe is its low wettability on Ti CN particles during liquid phase sintering,which hinders the processing of the cermet.In this article,W6Mo5Cr4V2 high speed steel has been chosen as metallic matrix of Ti?C,N?based steel bonded carbide,the mass fraction of Ti?C,N?was 36%.The influence of alloying elements and carbon content in the liquid phase formation has been investigated.The alloy elements and its carbide can improve the organization and improve the mechanical performance of the alloy.This paper focuses on the effects of preparation process,the carbon content and heat treatment process to the microstructure and the mechanical properties.The raw material milled 12 h by high energy planetary in the argon atmosphere obtain the best results.The raw material have better crushing effect,more uniform,and the oxygen content increasing the minimum of only 1.3%,the carbon / nitrogen ratio remained the same level of raw material powder.With the increase of sintering temperature,the mechanical properties of Ti?C,N?based steel bonded carbide tend to increase first,and then decrease.When the sintering temperature is1450 ?,the mechanical properties have emerged a turning point,the hardness is 1265 HV30 and the fracture toughness of the sintered body is11MPa·m^1/2.In this case,the alloy have the best microstructure,and being similar to the core-rim structures of cermet.The carbon contenthas great influence on the microstructure and sintering mechanism of the alloy.When the carbon content is 0.9%¹.1%,alloy liquid phase sintering,The part of Ti?C,N?particles of dissolved in the liquid phase,and the alloy elements in steel matrix forming solid solution,precipitated out when cooling from the steel matrix.the precipitated phase distributed in undissolved Ti?C,N?particles,formed typical core-rim structure,which improving wettability of the steel matrix to hard phase.One advantage of using Fe as a matrix is the ability to be hardened by heat treatment.Therefore the heat treatment conditions?austenitizing followed by hardening and double tempering?to increase the hardness of the sample have been established.When the heat treatment process are quenching from 1170 ? and double tempering from 520 ? in the atmosphere of argon,Ti?C,N?based steel bonded carbide get a better effect of heat treatment,in which the hardness increased by 21% to reach1530 HV30 and the fracture toughness increased by 38% to reach 15.2MPa·m^1/2.In addition,the oxidation behavior of Ti?C,N?based steel bonded carbide as sintered and after heat treatment has been studied.The oxidation surface presents three different layers,the formation of the inner layer are TiO--₂ and FeTiO₃ during the oxidation process,the intrusion of oxygen on the inner laye was prevented,and the rate of increase in the oxidation rate was obviously decreased.