Degradation Behavior of TiN Coatings with Different Thicknesses after a Pulsed Laser Thermal Shock Test

The degradation behavior of TiN coatings with different thicknesses deposited on Inconel 617 substrates was investigated in terms of surface and interface microstructures after pulsed laser thermal shock. The specimens with coating thicknesses of 1.0 and 4.5 mu m were exposed to repetitive laser shock using a pulsed laser ablation system (LSX-213). The TiN coating with a 1.0 mu m thickness contained cracks along the columnar grains in the coating layer, and spalling and delamination with interface cracks appeared with an increase in the number of ablations. In contrast, the 4.5 mu m thick TiN coating still maintained adhesion to the substrate until the substrate elements dissolved out to the surface. Surface and cross-sectional observation showed that the pulsed laser seems to simultaneously induce normal and shear stress to the surface at the ablated spots with high thermal stress.