Microstructure and high temperature wear behaviour of in-situ TiC reinforced AlCoCrFeNi-based high-entropy alloy composite coatings fabricated by laser cladding

AlCoCrFeNiTix (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) HEA coatings reinforced by in-situ TiC particles were successfully prepared on AISI1045 steel via laser cladding. The coatings are made up of two BCC phases identified as Fe-Cr and Al-Ni phases, and a few in-situ TiC phases with a shape of granular in micro-nano scale. Ti element prefers to dissolve into the Al-Ni phase and refines the equiaxed grains. The AlCoCrFeNiTi1.0 HEA composite coating with the highest volume fraction of TiC particles phase (2.6%) exhibits the highest average microhardness (860.1 HV0.3). It is found that the composite coating is strengthened by the effect of solid solution strengthening, dispersion strengthening, and fine-grain strengthening. The wear behaviour of the coatings was tested at 25 °C and 600 °C, respectively. The micromorphology and chemical composition analysis of the wear scars show that oxidation wear occurs in addition to adhesive wear during the wear process at 600 °C. The oxidation products are identified as Al2O3, CoO, Cr2O3, Fe2O3, Fe3O4, and NiO in terms of the calculation of flash temperature and Gibbs free energy. The calculation results of wear rates show that the AlCoCrFeNiTi1.0 composite coating exhibits the best wear resistance.