Laser surface treatment of high-speed steel: Presence of tic particles at the surface

Laser treatment of a high-speed steel surface is carried out and metallurgical and morphological changes in the laser-treated layer are examined using SEM, EDS and XRD. A carbon film of 50 μm thickness and containing 5% TiC particles is formed at the workpiece surface prior to the laser treatment process. The carbon film formed at the surface enhances the absorption of laser irradiation and retains TiC particles at the workpiece surface. The residual stress formed at the laser-treated surface is determined using the XRD technique while the indentation tests are carried out to measure microhardness and fracture toughness of the resulting surface. It is found that ε-Fe ₃N, and ε-Fe ₃ (N,C) compounds are formed at the laser-treated surface, which are attributed to the presence of carbon film and high-pressure nitrogen-assisting gas. The fracture toughness of the laser-treated surface reduces because of the increased hardness and dense layer formed at the surface vicinity.