Influence of pulse width in laser assisted texturing on moly-chrome films

Continuous micro-channels were formed on the surface of the automotive piston rings using two different lasers, namely nanosecond and femtosecond pulsed laser. Tribology measurements were conducted to compare the friction properties of the samples fabricated with the laser pulse width of nanosecond and femtosecond order. The femtosecond laser ablation comparatively minimized the re-deposition layer, heat affected zone around the micro-channel compared to the nanosecond laser ablation. Owing to the localized material ablation, the compressive residual stress was not altered with femtosecond laser processing. The friction test was conducted using reciprocating type friction measurement setup for the loads ranging from 10 to 130 N. The friction coefficients of all the textured samples were reduced compared to the non-textured samples. Furthermore, it is observed that the average friction coefficient was low with the femtosecond laser textured samples compared to that of the nanosecond laser textured samples of the same dimensions. The results show that the thermally induced defects while using the nanosecond laser ablation might have influenced the tribological properties.