Gas Nitriding of the Near-Beta-Titanium Alloy

Abstract

The present research investigates the nitriding kinetics of the near-beta-titanium alloy of Ti-Al-Nb-Fe-Zr-Mo-V system at 750, 800, and 850°C in gaseous nitrogen at 10 5 Pa for 2, 4, and 8 h. The parabolic coefficient kp of the layer’s growth rate and the nitriding activation energy E are set as the kinetic parameters of the nitrided layer’s growth. The activation energy for the formation of a nitride layer is ~108 kJ/mol. The authors discuss the morphology of the nitride layers as well as their roughness and surface hardness. The study determines the effective diffusion coefficient for the growth of diffusion layers in the temperature range of 750...850°C: Def = D0 × exp (– E/RT), where D0 = 0.0177 m 2/s; E = 215.7 kJ/mol. The friction coefficient of the disk from near-beta-titanium alloy with a bronze block is lowered by significantly more than 10 times after gas nitriding, and the temperature in the friction zone is reduced by 2.5 times.

Keywords

• near-beta-titanium alloy
• nitriding
• kinetics
• diffusion
• microhardness