Effect Of Discharge Intensity On Microstructure And Properties Of WC-8Co Cemented Carbide Prepared By Plasma Milling

WC-Co-based cemented carbide is mainly composed of hard phase WC and binder phase Co.It has high hardness,wear resistance and relatively good toughness,So widely used in rock drilling and cutting tools.However,with the rapid development of industry,the contradiction between the hardness and toughness of the traditional WC-Co cemented carbide makes it more and more unable to meet the needs of industrial applications.So,the development of"double high"WC-Co cemented carbide with high hardness and high toughness has become very urgent.At present,the common"double high"WC-Co cemented carbide mainly includes the following types:functional grade WC-Co cemented carbide,double-scale WC-Co cemented carbide,plate-shaped WC-Co cemented carbide and ultrafine crystalline WC-Co cemented carbide.In the early stage,the research group prepared a cemented carbide with a plate-like WC structure by using W,C and Co as raw materials in combination with plasma milling technology and carbonization sintering.Therefore,the purpose of this paper is to determine the appropriate plasma discharge parameters by studying the effects of plasma discharge intensity on the milling effect and the microstructure and properties of the one-step WC-Co cemented carbide.Then,preparing high-performance plate-shaped WC-Co cemented carbide with the plasma discharge parameters.At the same time,inspired by this,this paper also attempts to prepare ultra-fine grained WC-Co cemented carbide with WO₃,C and Co as raw materials combined with plasma milling technology and in-situ reduction method.Firstly,this paper sets up five kinds of discharge parameter matching to study the effect of plasma discharge parameters on the milling effect of W-C-Co powder and WO₃-C powder,respectively.The results show that the change of discharge parameters will affect the plasma discharge intensity,and the stronger the plasma discharge intensity,the larger the specific surface area of the milled powder,the finer the crystal grains,the higher the activity and the lower the carbonization temperature.Among them,the discharge parameters with the strongest plasma discharge intensity are matched:the dielectric barrier layer is a plastic king and its radius is 3 mm,and the discharge pressure is 5 x 10³ Pa.Secondly,the W-C-Co composite powders milled by ordinary mill,the weakest plasma discharge intensity and the strongest plasma discharge intensity were used for compression molding and low-pressure sintering to prepare WC-Co cemented carbide.The WC morphology,alignment and mechanical properties of the three cemented carbides were analyzed and compared.The results show that the plasma discharge ball milling is beneficial to promote the growth of W-C-Co composite powder into aligned WC cemented carbide during sintering process,and the stronger the discharge intensity,the deeper the orientation.Moreover,the WC-8Co cemented carbide prepared by the strongest plasma discharge intensity has the best comprehensive performance,and its transverse rupture strength and hardness are 3567 MPa and HRA 92.7,respectively.Finally,the process of synthesizing WC powder by in-situ reduction method using WO₃,C and Co as raw materials and preparing WC-8Co cemented carbide was explored.The results show that under the milling process with the strongest plasma discharge intensity,the suitable carbon content,in-situ reduction temperature and time of in-situ reduction of WC powder are 18wt%,1150°C and 1h,respectively,and the synthesized WC powder particle size is between 100²00nm.Moreover,the WC grain size distribution in WC-8Co cemented carbide prepared by in-situ reduction method is between 450 and 600 nm,which belongs to the ultrafine grain category.The density of WC-8Co cemented carbide is 99.2%,the hardness is HRA90.1,and the transverse rupture strength is 2042 MPa.