Evolution of microstructure and mechanical properties of in situ synthesized TiC-TiB2/CoCrCuFeNi high entropy alloy coatings

The aim of this paper was to explore a one-step in situ method to synthesize the TiC-TiB2 reinforced CoCrCuFeNi high entropy alloy composite coatings. In this method, the composite coatings were prepared by plasma transferred arc cladding process using Ti, B4C, Co, Cr, Cu, Fe, and Ni powder mixture as precursors. The effects of CoCrCuFeNi(Ti, B4C)x (x in molar ratio, 0.1 ≤ x ≤ 0.5) additions on the structure and mechanical properties of the coatings were investigated. For 0.1 ≤ x ≤ 0.2, the coatings induce the formation of face-centered cubic (FCC) and body-centered cubic (BCC) plus TiC structures. Further addition of x content (0.3 ≤ x ≤ 0.5), promotes high volume fraction of dual-phase TiC-TiB2 embedded in FCC and BCC matrix. There are also corresponding variations in mechanical properties with structural evolutions. For CoCrCuFeNi(Ti, B4C)0.1 coating, the nanohardness (H) and Young's modulus (E) are 4.19 and 234 GPa, respectively. These properties are further improved as function of x content (H = 9.14 GPa and E = 261 GPa are achieved in CoCrCuFeNi(Ti, B4C)0.5 coating). The mechanical hardening is accompanied with an increase of the ratio of hardness to elastic modulus (H/E), the yield pressure (H3/E2) and the elastic recovery (η value). An attempt has been made to co-relate the wear resistance of the coatings with H/E ratio and η value.