A New Tribo-Characteristic Improvement Technique by Ultra-Short Pulsed Laser Irradiation in PAO Oil

With the pursuit of high-precision and high-efficiency machining, laser-assisted machining technology has attracted more and more attention. Especially, ultra-short pulse laser irradiation can facilitate a quite high cooling rate and produce a local active space, which can make the surface modification realized without any removal. In this study, a novel tribo-characteristic improvement technology using ultra-short pulse laser irradiation in oil, with the hydrocarbon composition in oil as a carbon source, was proposed, to realize the surface modification of the workpiece in the same process with machining. Herein, a Ti-6Al-4V disk was irradiated using a pico-second laser in PAO oil under 4 different conditions with changed effective irradiated laser pulses and scanning modes. Besides the uniform laser irradiation, patterning irradiation was also conducted. From the results of the reciprocating friction tests, compared to those uniformed irradiated specimens, patterning irradiation processed surfaces show obviously more stable friction than the as-received metal surface. More importantly, much longer lifetime has been obtained, indicating the enhanced wear resistance. According to the investigation of hardness distribution, laser-induced thermal strain in the patterning irradiation method is considered to be an important factor of wear resistance improvement.