Tribological performance improvement of titanium through laser-induced oxygen and nitrogen incorporation: experimental and molecular dynamics study

Titanium and its alloys have a pronounced tendency for adhesive wear and surface degradation under mechanical stress, severely limiting their widespread application in machine elements and components. A durable and efficient surface treatment for improving their wear resistance remains a major challenge. This study puts forward a cost-effective laser surface modification technique to enhance the tribological properties of commercially pure α-titanium (grade 1) by introducing interstitial oxygen and nitrogen. The process involves melting the titanium surface with a nanosecond pulsed laser in air, nitrogen, or argon atmosphere, followed by a smoothening step in argon atmosphere. Comprehensive characterisation using X-ray diffraction, electron microscopy, nanoindentation, and tribological testing reveals that interstitial oxygen and nitrogen significantly increase surface hardness and suppress adhesive wear by saturating titanium’s valence bonds and reducing surface reactivity. The modified surfaces exhibit improved wear resistance and more stable friction behaviour under lubricated conditions, with minimal running-in and wear volume. The increased wear resistance has its origins at the atomic scale and is attributed to the role of oxygen and nitrogen occupying interstitial positions in the titanium lattice, as well as grain boundary deformation, as suggested by molecular dynamics simulations of nanoscratching. ... mehrThe merged experimental and computational approach establishes a solid foundation for tailored surface engineering strategies that optimise titanium’s wear performance for future engineering applications.