TiC-xNi composite coatings by high-frequency induction-heated combustion synthesis and their corrosion resistance in molten brass

Abstract

TiC-xNi composite coatings (x = 10, 20, 30, 40, and 50 wt%) were synthesized in situ on H13 substrates using high-frequency induction-heated combustion synthesis (HFIHCS). The parameters of induction current and hot-press sintering duration were systematically optimized. The effects of nickel content on the microstructural characteristics, porosity levels, and bonding performance of the TiC-xNi coatings fabricated via HFIHCS, as well as their corrosion resistance in molten brass environments, were investigated. The findings indicated that optimal microstructural integrity and porosity were achieved with an induction current of 500 A and a hot-press sintering time of 30 s. The surface porosity and TiC grain size exhibited a decreasing trend with increasing nickel content, while the internal porosity demonstrated an inverse relationship. The observed increase in lattice constants of the TiC phases in the TiC-xNi coatings (x = 10, 20, 30, and 40 wt%) relative to the standard value can be attributed to the synergistic effects of elevated argon pressure and a substantial presence of solid solution elements. The higher temperature of the molten brass resulted in a corrosion surface of the H13 steel that comprised an outer layer of adhesive brass and an inner mixed layer of immersed brass and substrate material. The corrosion layer of the TiC–10Ni coating was characterized by a thick outer layer of mixed oxides and an inner layer of TiC oxides, with the native TiC particles becoming indistinguishable. Conversely, the surface of the TiC–20Ni coating was covered by a thin, singular corrosion layer composed of oxides, brass, reaction alloys, and discernible native TiC particles. The presence of narrow and wide nickel zones in the pristine coating is attributed to the regulation of diffusion channel closure and patency between the coating and the molten brass, respectively.