Preparation And Properties Of TiC Particle Reinforced Co-crystalline High Chromium Cast Iron Matrix Composites

High chromium cast iron（HCCIs）based composite materials were widely used in friction and wear conditions due to their excellent mechanical properties.However,with the development of society,some infrastructures gradually show diversified requirements for materials of parts,which require materials to have better performance and can adapt to a variety of harsh working conditions,such as more worn-out mineral conveying pipelines and corrosiveness.Primary M₇C₃（Fe₇C₃,Cr₇C₃）as the main strengthening phase in HCCIs alloy,has an important influence to the properties of composite.But,the primary M₇C₃carbides are distributed in long strips in the matrix,which easily leads to anisotropic properties of the composite material due to the large size of primary M₇C₃carbides.It was easy to crack under cyclic stress or large impact load,and the reliability was difficult to guarantee.Therefore,to explore the refinement and distribution of M₇C₃carbides and further improving the mechanical properties of the alloy have become a key point in performance research of eutectic HCCIs.According to the first principle,MC carbide has a refinement effect to the size of primary M₇C₃carbide.Before starting the research,a large number of pre-experiments were carried out on the eutectic HCCIs,and the precise phase diagram of the quaternary alloy was obtained by combining its element composition and preparation process.Based on the phase diagram,the composite material preparation process parameters were designed,the composite materials with different TiC content were prepared by vacuum melting method,and the microstructure of TiC particles reinforced HCCIs,the size and volume fraction of the reinforced phase,and the phase were studied systematically.It is found that addition of the4.8%Ti content in alloy can effectively deprive the C content in the primary M₇C₃carbides,which reduced the volume fraction（23%-18%）and size（64-47μm）of the M₇C₃carbides in the alloy.And the size change of TiC was not obvious effect with the increase of Ti content.The primary M₇C₃carbides were distributed in long strips in matrix,and some M₇C₃carbides have a irregular shapes.TiC particles were approximately spherical.When the Ti content was greater than 1.6%,TiC tends to aggregate.In order to further understand the effect of TiC particles on the performance of HCCIs,this paper carried out three-body abrasive wear,normal temperature abrasive wear,erosion wear experiments and corrosion resistance tests on samples with different TiC content.It was found that addition a certain content of TiC significantly enhances the mechanical properties of as-cast specimens,while the heat-treated specimens have poor toughness due to the presence of TiC particles and refined M₇C₃carbides,and the wear resistance is lower than that of the as-cast samples with higher TiC content.Meanwhile,TiC and primary M₇C₃carbide have a certain weakening effect on the corrosion resistance of the composite material,it is mainly due to the poor wetting in the interface between TiC and M₇C₃carbide and the matrix,some small holes and gaps in the phase boundary provide channels for the diffusion of the anion,and the severe corrosion between TiC and the matrix.Under the high temperature conditions,with the extension of the oxidation time,the oxide has a growth process.Although the oxidation rule of each component in the alloy is:TiC>M₇C₃>matrix,after 100h oxidation at 1000℃,due to the higher content of M₇C₃and matrix,TiO₂was covered by more hexagonal Cr₂O₃and long strips of Fe₃O₄.