Degradation behaviour of TiN and TiCN coatings after laser ablation

Titanium nitride (TiN) and titanium carbon nitride (TiCN) coatings deposited on Inconel 617 substrates after pulsed laser thermal shock were investigated in terms of morphological observations and atomic concentration profiling in order to compare their deterioration behaviour. The specimens were prepared by an arc discharge technique with a coating thickness of 2.0 mu m and ablated with increasing laser pulses using an Nd:YAG pulsed laser ablation system. Surface cracks and pores appeared on the TiN coating subjected to laser ablation, and spalling of the coating layer occurred with large crack propagation, whereas the TiCN coating showed less surface degradation. The coating thickness for both specimens decreased as the laser pulses increased, and interface cracks with delamination formed in the TiN coating. Depth profiling indicated that atoms of the substrate diffused to the surface by thermal stress, and three-dimensional mapping for roughness measurement identified higher thermomechanical stress resistance of the TiCN than the TiN.