Preparation And Mechanical Properties Of Iron Matrix Composites Reinforced By Ni Coated SiC Composite Powders

Silicon carbide particles reinforced metal matrix composites, which combinethe high strength and hardness of silicon carbide with the toughness and workabilityof metal materials, gradually become a kind of composite materials with low-costand high wear resistance.Ni coated SiC composite powders were prepared by in situ chemical deposition,which used NiCl2·6H2O as nickel source and N2H4·H2O as reducing agent,respectively. Then, the SiC(Ni)/Fe composites were prepared by vacuum hot-pressedsintering. The microstructure and phase composition of Ni-coated SiC compositepowders and SiC(Ni)/Fe composites were characterized by Scanning electronicmicroscope (SEM), Energy dispersive X-ray spectroscopy(EDS), X-Ray diffraction(XRD), Fourier transform infrared spectroscope (FT-IR) andThermo-gravimetric/Differential thermal Analyzer(TG-DTA). The effects ofsintering temperature, pressure and time on the mechanical properties of SiC(Ni)/Fematrix composites were studied by testing the density, vickers hardness, bendingstrength and force-displacement of the composites. By studying mechanicalperformance and organization structure of SiC/Fe and SiC (Ni)/Fe composites withdifferent SiC contents, the friction and wear mechanisms, fracture morphology anddensification mechanisms of SiC/Fe and SiC (Ni)/Fe composite material werediscussed, respectively.The results indicated that the nickel hydrazine complex precursor prepared incomplexation reaction time of5min can obtain the best coated composite powders at50℃water bath temperature, and nickel hydrazine complex precursor prepared incomplexation reaction time of2h can obtain the best coated composite powders at60℃water bath temperature, respectively. By a series of contrast experiments, it isshown that the best sintering system of SiC(Ni)/Fe composites is1000℃,45minand40MPa. The sintering sample with5wt%of SiC(Ni) has the best mechanicalproperties. The density, Vickers hardness, bending strength and displacement is 7.1564g/cm3,3.39GPa,1120MPa, and0.4025mm, respectively. Compared with theSiC particles without Ni coating, the reinforced iron-based composites containingNi-coating particles showed higher relative densities and better mechanicalproperties. In addition, The wear forms of SiC(Ni)/Fe and SiC/Fe compositematerials are transformed from adhesive wear to abrasive wear and surface fatiguewear with the increase of the content of SiC. It is supposed that Ni-coated SiCcomposite powders were beneficial for the microstructure and properties of thereinforced iron-based composites due to promotion of neck formation and growthbetween SiC and iron powders during sintering, which enhanced the relative densityof sintered compact and the bonding strength between SiC particles and iron matrix.Therefore, SiC(Ni)/Fe composites have more dimples and tear ridges. Otherwise, theexistence of Ni transition layer can interdict the direct contact of SiC particles, thusreduce the formation of microcrack at particles aggregation, which is advantage toimprove mechanical performance of SiC(Ni)/Fe composites.