Research On The Microstructure, Properties And Thermal Shock Resistance Of Nano-TiN Modified Ti(C,N)-based Cermets

Ti(C,N)-based cermets have been widely concerned and researched because oftheir excellent physical properties and mechanical properties since Ti(C,N)-basedcermets are produced. And Ti(C,N)-based cermets have been widely used in thepractical application. In this paper, based on the research of the mechanicalproperties, physical properties, microstructure and the propagation behavior ofcracks, the thermal shock resistance of Ti(C,N)-based cermets was investigatedsystematically.In the first part of the thesis, Ti(C,N)-based cermets with different WCaddition were prepared by conventional powder metallurgy techniques and vacuumsintering. The effect of WC content on microstructure and mechanical properties ofcermets were analyzed by the ways of X-ray Diffraction (XRD), Scanning ElectronMicroscope (SEM), Energy Disperse Spectroscopy (EDS), et al. The results showthat the grain is refined with appropriate WC addition. The microstructure ofTi(C,N)-based cermets with15%WC addition has the finest grain and distributesuniformly, but when the addition of WC exceeds15%, the grain becomes coarseagain. The bending strength of cermets increases with the increasing of WCaddition. The hardness and fracture toughness firstly increase and then decreasewith the increasing of WC addition, and the cermets have the highest hardness with10%WC addition, the best fracture toughness with15%WC addition.Secondly, the effect of WC addition, thermal shock cycles and thermal shocktemperature on the thermal shock resistance of Ti(C,N)-based cermets wereinvestigated by the method of quenching-strength. The experimental results showthat the critical temperature of thermal shock residual strength increases with theincrease of WC addition. The thermal shock residual strength decreases with theincreasing thermal shock cycles, and the decline rate of strength rises with theincreasing temperature. The propagation rate of thermal shock crack wasresearched by the indention-quenching test. The cermets have the slowestpropagation rate with15%WC addition.The thermal shock performance of cermets was calculated by the calculatedphysical properties and experimental mechanical properties through the thermal shock resistance evaluation theory of ceramic material. The calculated results ofthe thermal shock resistance consistent with experimental results, which states thatthe thermal shock resistance has a compact relation with the physical performanceand mechanical properties...