Fabrication of microcone arrays on Ti6Al4V by nanosecond laser nitriding

The application of titanium alloys still faces some challenges such as relatively low hardness and insufficient wear resistance. Nanosecond pulsed laser irradiation in a nitrogen atmosphere has proven to be effective for fabricating micro/nano structures on titanium alloys, enhancing surface hardness and wear resistance. However, micro/nano structures produced by line-by-line laser scanning often exhibit directional differences and surface defects such as re-deposited particles and pores. Herein, vertically crossed laser scanning in a nitrogen atmosphere was employed to address the directional difference, enabling the simultaneous fabrication of microcone arrays and nitriding layers on Ti6Al4V surface. To eliminate the surface defects on the microcone structure, laser surface finishing via defocused scanning was performed, followed by morphological analysis, bonding force evaluation, and tribological performance testing. The results showed that the area percentage of re-deposited particles on the laser-finished microcone array surface decreased from 24 % to 5 %. The bonding force of the nitriding layer was assessed using linear loading scratch tests, and the highest value of 69 N was obtained. To investigate the wear resistance of the laser-finished microcone array surface, friction and wear tests were performed. From 25 °C to 600 °C, nearly no wear grooves were observed on the tested surfaces, demonstrating excellent high-temperature wear resistance. The wear mechanism was mainly related to the cutting action of the microcone structures on the counterpart ball. This study advances the fabrication of micro/nano structures and simultaneous nitriding on titanium alloys, demonstrating the significant potential for practical applications as surface contact materials.