Research On Preparation And Hot Deformation Of M42 Powder Metallurgy High Speed Steel

High speed steel is a kind of high carbon and high alloy ledeburite steel containing a large amount of alloying elements,also known as front steel.It has high hardness,toughness,red hardness,and wear resistance.It is mainly used in tools,molds and some heat resistant and high-temperature resistant parts.Powder metallurgy high speed steel（PMHSS）avoids the disadvantages of easy segregation of carbides in molten cast high speed steel,which causes mechanical properties reduction and heat treatment deformation,and overcomes the limitation of the shape and size of spray-formed products.Therefore,its comprehensive performance is superior.However,the current PMHSS preparation process is complicated and the equipment requirements,production cost,and the price is high,which hinders its application and development in the industry.In this paper,the Fe,WC,Mo₂C,Cr₃C₂,VC and Co powders are used as raw materials to prepare M42 PMHSS by cold pressing and solid-phase sintering in protective atmosphere.This method reduces the production cost of PMHSS to a certain extent.The preparation process of M42 PMHSS was explored.Through the density test,pore and microstructure observation,hardness and bending strength test,etc.,the effect of carbon content and sintering temperature on M42 PMHSS was studied.The influence of hot deformation parameters on the hot deformation behavior of M42 PMHSS is studied,and its hot processing diagram is established.The main research results are as follows:When the carbon content is 0.2%,the carbon content of the sintered billet is 1.13%,which is in line with the carbon content range of M42 PMHSS.When M42 PMHSS with 1.13%carbon content is sintered at 1140～1180℃,it is found that the relative density and hardness gradually increase with the increase of sintering temperature,and the grains gradually grow up.When the sintering temperature is 1180℃,its relative density is 98.39%,close to full density,and its hardness is HRC 56.2.With the increase of sintering temperature,its flexural strength first increases and then decreases,reaching a peak at 1160℃.According to the microstructure and mechanical properties,the optimal sintering temperature of the M42PMHSS is 1160℃,and the corresponding hardness is HRC 53.3,and the bending strength is2035 MPa.The flow stress of M42 PMHSS increases rapidly with the increase of strain in the initial deformation stage.With the increase of deformation,the growth rate of flow stress slows down,and then reaches the peak value and finally gradually decreases.The flow stress increases with the increase of deformation temperature and the decrease of strain rate.A constitutive equation characterizing the high temperature compression flow behaviors of M42PMHSS is established.The flow stresses predicted by the constitutive equation are basically consistent with the experimental results.The correlation coefficient between the predicted and experimental results is 0.99048,and the average absolute relative error is 3.82%;The hot processing map of M42 PMHSS was also established,and the optimal hot processing parameters were obtained as the strain rate of 0.1～1 s^-1and the deformation temperature of1050～1100℃...