Femtosecond laser processing of nitride-based thin films to improve their tribological performance

The ability of femtosecond laser pulses to pattern coated tribological surfaces in order to improve their wear behavior was investigated. Experiments were performed with a Ti:sapphire laser (wavelength: 800nm, energy density: 2J/cm2, pulse duration: 100fs) on TiN- and on TiCN-coated surfaces. Morphological analyses of the laser-treated surfaces were carried out and did not reveal any film delamination or other coating damage after laser processing. Tribological tests simulating rapidly increasing contact pressures under boundary friction were performed on both unpatterned and laser-patterned coated surfaces using a steel counter body. The patterned surfaces showed significantly better tribological performance with respect to stability and the value of the friction coefficient during testing. EDX analyses of the tested unpatterned samples revealed complete coating removal and material transfer from the counter body to the sample surface. In the case of the laser-patterned surfaces, only slight coating damage and an accumulation of debris from the steel counter body in the laser-induced pores were observe