Wear resistance performance of high entropy alloy–ceramic coating composites synthesized via a novel combined process

Abstract

Titanium nitride (TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTix high-entropy alloy (HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then, TiN ceramic coating on the AlCrFeNiTix bulk HEA containing the topologically close-packed (TCP) phase (σ phase, Laves phase, and Ti3Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis, Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear, which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTix alloy with the excellent hardness and wear properties.