In Situ Synthesis Of TiC/Ni₃Al Intermetallic Matrix Composites On Steel Surface

TiC-reinforced Ni₃Al matrix composites were fabricated as coatings on steel through SHS-Casting technology. The thermal explosion and its product micro-topography, microstructures, interfaces of the coating were analyzed by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy-dispersive spectrum (EDS) and transmission electron microscopy(TEM). The formation mechanism of the coatings as well as the dynamic process of liquid steel infiltration was discussed. Based on this, the affects of technological parameters on the coating microstructures was also analyzed.The experimental results show that TiC and Ni₃Al were the most stable phases in Ti-C-3Ni-Al system. The exothermic reaction of nickel and aluminum ignited the reaction of titanium and carbon. During reactions TiC was always in solid state and Ni₃Al in liquid state. The thermal explosion starting temperature of the 3Ni-Al-Ti-C system is independent of the TiC content. Ingredients and thermal explosion temperature were found to have obvious influences on the thermal explosion, morphology and raletive density of the products.TiC/Ni₃Al coating was formed on steel with high purity. No iron phase can be found in the coating surface. With increase in TiC content, TiC particulate became slightly coarser and the composite denser. Interface morphology varied with the TiC content of the coating. With TiC content increasing from 25wt% to 45wt%, the composite is densely formed with absence of pores and morphology of the interface changes from integral form to detached form. Ni,Al,Ti,Fe and microhardness were revealed to have graded distribution from the coating to the interface.The functions of thermodynamics and dynamics in the process of coating formation are integrative and reactive. The existence of Liquid Ni₃Al contributes to the infiltration of liquid steel. Technological parameters have obvious influences on coating microstructures. The microstructure of the coating is revealed to be denser with higher pouring temperature, lower perform density and higher TiC contents.