Preparation And Properties Of Iron Matrix Composites Reinforced By Cu Coated SiC Particles

Silicon carbide is an ideal reinforced material for composites due to its advantages such as low price, high hardness, good resistance to wear and corrosion, etc. Iron, which has good strength and toughness, is one of the most commonly used metal materials in modern industry. The addition of the reinforced particles with low density, high strength and high rigidity into the iron matrix can reduce the density of the material as well as increase its elastic modulus, hardness, wear resistance and high-temperature performance. Thus, the combination of these two materials will bring a new metal matrix composite with low-cost, good comprehensive properties and high wear resistance.In this study, surface treatment technique such as high-temperature oxidation, acid dipping and alkaline wash was adopted separately on silicon carbide particles. Replacement reaction method and decomposition-reduction reaction method were used to generate Cu coating on the surface of silicon carbide, which, in order to improve the wettability and physical and chemical compatibility between silicon carbide and iron. Based on the powder metallurgy method, spark plasma sintering (SPS) and hot-pressing sintering (HP) were used respectively in fabrication of SiCp(Cu)/Fe composite. The microstructure and the interface characteristics of SiCp/Cu composite powder and SiCp(Cu)/Fe composites were analyzed by means of DTA-TG, XRD, SEM, EDS, OM techniques and so on. Archimedes method, microhardness instrument, three point bending method and wear test method were used to study the properties and mechanism of SiCp(Cu)/Fe composites. The influences of sintering temperature and pressure, the content of reinforcement and other different technological conditions on the properties of the composites were investigated.The results indicated that for the same silicon carbide particles, the effect of the Cu coating prepared by decomposition reaction method was better than that by reduction reaction method. In addition, as a result of the high-temperature oxidation, the edges of silicon carbide particles were passivated and a layer of silicon dioxide film was generated on the surface of silicon carbide particle. Consequently, SiCp/Cu composite powder can be obtained. The surface of silicon carbide particle which treated by alkaline wash after oxidation and acide dipping was cleaner and more rough than that only treated by high-temperture oxidation, moreover, the specific surface of the particle was increased, which resulted in a compact layer of Cu coating. The properties such as relative density, microhardness, bending strength and wear resistance of SiCp(Cu)/Fe composites which fabricated by spark plasma sintering achieved to the best level under 950℃and 25MPa. In addition, with the increase of the SiCp(Cu) content, these properties first increased then decreased. And the best properties were obtained at the content of 6wt.%, the relative density was 99.1%, the microhardness was 440.6HV, the bending strength was 689.2MPa and the abrasion loss was 1.099mg/m. Furthermore, the interface bonding strength between silicon carbide and iron matrix was improved due to the Cu coating on the surface of silicon carbide particles, which finally enhanced the comprehensive performance of the composites.