Electrospark Deposition of Hard, Wear-Resistant and Anti-Friction Coatings on γ-TiAl Substrates in a Controlled Gas Environment

Abstract

The development of hard, wear-resistant, and anti-friction Ti–Zr–Al-based coatings via electrospark deposition for the protection of Ti–48Al–2Cr–2Nb alloy using a Zr electrode in controlled gaseous environments was carried out. In the Ar atmosphere, a 50 µm thick coating based on β-Zr solid solution with low values of Young’s modulus (83 GPa) and of hardness (6.2 GPa) is formed. In C₂H₄, a coating with a β‑Zr_ss matrix, in which (Zr,Ti)C grains (20–400 nm) of the carbide phase and the Laves phase h-Zr₂Al are uniformly distributed, is formed, characterized by moderate hardness (10.6 GPa) and Young’s modulus (144 GPa) values. In the N₂ atmosphere, a bilayer coating based on (Ti,Zr)N grains with a TiAl matrix in the lower and TiAl₃ in the upper layer of the coating is formed. The upper layer is characterized by a higher content of (Ti,Zr)N grains, with the grain size being smaller than in the bottom layer. The coating has high wear resistance, a low friction coefficient (0.12), high hardness (14.6 GPa) and Young’s modulus (40 GPa). The thickness of the coatings deposited in C₂H₄ and N₂ atmospheres was 25–35 μm.