ZrC reinforced refractory-high-entropy-alloy coatings: compositional design, synthesis, interstitials, and microstructure evolution effects on wear, corrosion and oxidation behaviors+

Abstract

A BCC-structural refractory-high-entropy-alloy (RHEA) composition of (TiZrNb)14AlMo (Al6.25Mo6.25Ti29.2Zr29.2Nb29.2, at.%) was designed by cluster-plus-glue-atom model. Its bulk and C-contained coatings were successfully achieved by arc-melting and laser-cladding techniques, respectively. The C interstitials were also introduced into RHEA coatings to investigate the effect of microstructure evolution on wear, corrosion and oxidation behaviors. The experimental results show that the bulk RHEA and its coating are composed of a single BCC solid solution. With the increasing additions of C atoms, the phase composition transforms into BCC solid solution and MC carbide plus HCP-α phase. The finer microstructure and slighter intergranular segregation render the RHEA coating with higher hardness (~431.3 HV0.2), compared with the bulk RHEA. Besides, the C interstitials effectively enhance hardness and wear resistance. While C content increasing up to 0.8 at.%, the C2 coating shows high hardness of 570.2 HV0.2 and low friction coefficient of 0.56. However, excessive C addition is deleterious to the corrosion resistance. In addition, RHEA and its C-free coating possess poor oxidation resistance mainly ascribed to the porous and much cracked oxide film. The additions of C atoms effectively improve the oxidation resistance. As for the C2 coating, the oxide gain decreases into 3.03 mg·cm−2.