Laser removal of TiN from coated carbide substrate

Sustainable manufacturing requires the extended usage of materials and reuse of hard metal tooling. In general, titanium nitride (TiN) coating gives enhanced hardness and wear resistance to the surfaces of engineering tools. However, the high hardness makes it difficult to re-grind or refurbish TiN-coated materials, especially TiN-coated cutting tools. This paper presents the results of laser decoating of TiN from TiN-coated tungsten carbide (WC) substrates. Laser decoating was performed using a KrF excimer laser. The effect of laser fluence, number of pulses, frequency, scanning speed and beam overlap on the decoating performance was investigated in detail. A two-dimensional symmetric finite element model (FEM) was established to elucidate the temperature and stress fields created during the laser decoating process. Successful laser decoating of TiN coating from the WC substrate was demonstrated. It was found that decoating with a laser fluence of 4 J/cm², scanning speed of 2 mm/s, frequency of 25 Hz and a beam overlap of 91% gives best results for removing an area of TiN coating to its 3 μm thickness. The surface roughness of the best samples was found to be in the order of 0.8–0.9 μm Ra. The experimental and FEM investigation suggested that the decoating of TiN follows combined explosion and evaporation mechanism.