A study of Ni3Al coating on carbon steel surface via the SHS casting route

A nickel aluminide (Ni3Al) coating on a carbon steel surface was fabricated by the self-propagating high-temperature synthesis (SHS) casting route. Co ating phases were determined by using X-ray diffraction (XRD). The microstr ucture of the coating and bonding interface between the substrate and the c oating, and the distribution of elements adjacent to the interface, were an alyzed by using electron probe microanalysis (EPMA). The microhardness of t he coating was measured. The tribological properties of the coating at diff erent elevated temperatures were investigated and the worn surfaces at diff erent temperatures were analyzed by EPMA. The elemental chemical state of t he worn surface was determined by using X-ray photoelectron spectroscopy (X PS). The results show that the coating was composed of Ni3Al phase, and tha t its microstructure was dense and pure. Elements had diffused mutually at both sides of the interface and a metallurgical bonding interface was forme d. The heat of the reaction coarsened the grain size of the substrate near the interface. The hardness of the coating is higher than that of the subst rate. Wear loss and friction coefficient of the coating vary with the testi ng temperature. The coating had a good resistance to oxidation at elevated temperature. Oxidation of the coating occurred as a result of friction at t he temperature of 873 K. The mechanisms of combustion synthesis of Ni3Al co atings on carbon steel substrates are discussed in detail. It is pointed ou t that the combustion temperature and the wettability between the product o f the reaction and the substrate are significant to obtain the coating. (C) 1999 Elsevier Science S.A.