Effect Of Rare Earth Oxides On The Microstructure And Properties Of TiC-based Cermets

TiC-based cermets exhibit excellent application prospects in fields such as oil and gas drilling and metal cutting due to their high hardness and wear resistance.However,traditional TiC-based cermets face problems such as service life attenuation when operating in harsh environments.The addition of rare earth elements can usually refine grain,remove impurities,and improve alloy density,achieving a comprehensive improvement in alloy performance.Therefore,this study focuses on the modification of typical commercial TM52 steel-based cemented carbide（TiC-based cermet,hard phase:48 wt.%TiC,binder phase:52wt.%high manganese steel）with trace amounts of different rare earth oxides（La₂O₃,Nd₂O₃,Yb₂O₃）.The study systematically investigates the effects and mechanisms of different types and contents of rare earth elements on the microstructure,mechanical properties,and service performance of TM52 through microscopic structure,performance characterization experiments,and phase diagram calculation（CALPHAD）method,providing an important foundation for further research to enhance the comprehensive performance of TiC-based cermets.The specific research contents are as follows:（1）By studying the effect of La₂O₃ on the microstructure of TiC-based cermets,it was discovered that La elements can be diffuse into the ceramic phase and binder phase of cermets after La₂O₃ decomposition at high temperature,thereby improving the overall microstructure of the cermets.As the content of La₂O₃ increases,the TiC lattice constant gradually increases,the annular phase ratio increases,and the average diameter of core particles decreases.Additionally,the influence of La element on the non-equilibrium solidification behavior of TiC-based cermets was calculated based on thermodynamic database.The results indicate that the La element is more inclined to be solid-dissolved in the ceramic phase.Furthermore,the addition of La element reduces the non-equilibrium solidification temperature,which results in the decrease of the core area of the core-rim structure and the increase of the rim area,thereby making the core-rim structure more uniform.（2）By examining the influence of Nd₂O₃ and Yb₂O₃ on the microstructure of TiC-based cermets,it has been discovered that Nd and Yb elements,which are decomposed by Nd₂O₃ and Yb₂O₃,can diffuse into the core-rim structure and binder phase of the cermets at high temperature.Unlike the La element,Nd and Yb exhibit no significant difference in solid solubility in cermets.Furthermore,as the content of Nd₂O₃ and Yb₂O₃ increases,the lattice constant of TiC gradually increases,the proportion of rim phase increases,the core phase area decreases,and the overall microstructure of cermets improves.The most effective particle refinement effect occurred when 0.5 wt.%Nd₂O₃ was added,as it reduced the core particle diameter from 0.64μm to 0.57μm.（3）By studying the effects of incorporating various rare earth oxides into TiC-based cermets,it was determined that addition of 0.3 wt.%La₂O₃ yielded the most significant improvement in density and fracture toughness,with values of6.12 g/cm³ and 6.0 MPa·m^1/2,respectively.Furthermore,the incorporation of rare earth oxides resulted in an increase in magnetic properties such as saturation strength（Hm）,residual magnetic induction strength（Br）,and coercivity force（Hc）in TiC-based cermets.Despite this,the impact of different rare earth oxides on the service performance of TiC-based cermets was explored,with varying effects on wear resistance.Of note,the wear resistance of TiC-based cermets decreased with the addition of rare earth oxides,with the least decrease observed in cermets with0.5 wt.%Yb₂O₃.However,TiC-based cermets with 0.5 wt.%La₂O₃ exhibited he best erosion resistance,showing an improvement of approximately 150%compared to samples without rare earth additions.