Effect of Vacuum Ion-Plasma Treatment on Surface Layer Structure, Corrosion and Erosion Resistance of Titanium Alloy with Intermetallic a2-Phase

Abstract

Results are provided for a study of the effect of vacuum ion-plasma nitriding on the phase composition, structure, microhardness, salt corrosion resistance, and erosion resistance of alloy Ti – 14Al – 3Nb – 3V – 0.5Zr with an original bimodal structure and different surface microgeometry. It is shown that with an increase in nitriding temperature from 550 to 650°C the content of Ti₂N nitrides in the surface layer increases and Ti₃AlN nitride in formed, which raises the microhardness but reduces the thickness of the hardened diffusion zone; pores appear in the surface at 650°C. Vacuum ion-plasma nitriding is shown to raise substantially the resistance of specimens of alloy Ti – 14Al – 3Nb – 3V – 0.5Zr with a polished surface to salt corrosion. Additional nitriding after deposition of a TiN coating improves ground specimens salt corrosion resistance. Vacuum ion-plasma nitriding with additional deposition of a TiN coating increases the resistance of specimens with polished and ground surfaces to erosive action.