Preparation and microstructure of CuNiTiZr medium-entropy alloy coatings on TC11 substrate via electrospark - computer numerical control deposition process

The CuNiTiZr medium-entropy alloy coatings were produced on TC11 titanium alloy substrate using the electrospark - computer numerical control deposition (ES-CNCD) process. The microstructure of the deposited coatings transforms from a BCC solid solution into an amorphous phase with the increase of the deposition layer number. The transformation is attributed to the high cooling rate of ES-CNCD and the increased atomic size difference (δ) of the coatings. The hardness of the 1/3/5/7/9-layer CuNiTiZr coatings are 614.1 HV, 484.2 HV, 588.5 HV, 709.1 HV and 581.2 HV, respectively, which are far greater than the hardness of TC11 (378.6 HV).