Effect of laser scanning speed on the surface characteristics and wear resistance of TiZrAlV alloy via laser gas nitriding

Abstract

This study investigated the effects of laser gas nitriding treatment on the Ti-20Zr-6.5Al-4V alloy using a closed IPG quasi-continuous laser. Various analytical techniques were employed to assess the phase composition, microstructural morphology and elemental distribution of the nitrided zone and the matrix at different scanning speeds (10 mm/s, 15 mm/s and 25 mm/s) when the laser power was 150 W. Additionally, vacuum friction and wear behavior were evaluated. The results indicate that following laser nitriding, the structure of the nitrided surface primarily comprises nitride dendrites and fine α grains. Element distribution tests confirmed that the nitrides present on the surface are predominantly Ti(Zr)_xN_y. Furthermore, as the scanning speed decreases, the hardness of the laser nitride layer progressively increases, with the maximum microhardness observed at a scanning speed of 10 mm/s, approximately 871 HV_0.5. The vacuum friction and wear results demonstrate that at a scanning speed of 10 mm/s, the COF value of the sample is only 0.337. Analysis suggests that laser nitriding treatment effectively refines the surface grains and generates hard nitrides, thereby enhancing the hardness and wear resistance of the alloy. Further analysis confirmed that the wear of the nitride layer primarily occurs through adhesive and abrasive mechanisms.