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

The development of hard, wear-resistant and anti-friction Ti-Zr-Al-based coatings via electrospark 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 a β-Zr solid solution with a low Young's modulus (E = 83 GPa) and hardness (H = 6.2 GPa) values was formed. In C2H4, a coating with a β-Zrss matrix, in which (Zr, Ti)C grains (20–400 nm) of the carbide phase and the Laves phase h-Zr2Al are uniformly distributed, was formed, characterized by moderate hardness (H = 10.6 GPa) and Young's modulus (E = 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 was 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 had high wear resistance, low friction coefficient (0.12), and high hardness (H = 14.6 GPa) and Young's modulus (E = 240 GPa). The thickness of the coatings deposited in C2H4 and N2 atmospheres was 25–35 μm.