Coatings with intrinsic stress profile: Refined creep analysis of (Ti,Al)N and cracking due to cyclic laser heating

A refined non-linear creep analysis of ceramic coatings has been performed by means of an improved substrate curvature technique in vacuum facilitating increased sensitivity by noise reduction. In this way the intrinsic stress profile may be derived from the time-dependent substrate curvature. Creep and stress parameters of 0.5 μm (Ti,Al)N-coatings have been found. At 500 °C the stress varies between − 1 GPa at the surface and + 0.2 GPa at the interface with the silicon substrate. From the onset of crack formation as observed in cyclic laser shock experiments a coating tensile strength of about 0.7 GPa is deduced. The number of cycles to cracking and delamination/spalling vs. maximum coating temperature as derived from creep simulation agrees quantitatively rather well with the experimental data. A rough estimate of the interface fracture toughness on WC/Co substrates yields 11 N/m as a lower bound.