Rapid surface nitriding of titanium alloy by a nanosecond fiber laser under atmospheric conditions

A modified surface layer using a Yb nanosecond fiber laser beam under atmospheric conditions was fabricated by applying a surface nitriding process on disc-shaped Ti–6Al–4V samples. On the generated surface, a melt layer comprising a TiN dendrite structure and a heat affected zone containing a needle-like α phase were detected. The modified layer exhibited optimal characteristics with the treatment at a laser output power of 12 W, resulting in a hardness of 12 GPa. The results of friction wear evaluation tests revealed that the layer exhibited superior abrasion resistance compared with an untreated Ti–6Al–4V substrate.