A sputtered nanocomposite coating was used to improve the lifetime of thermal spray instrumentation used in gas turbine engine applications. This sputtered coating was deposited directly onto a thermal sprayed bond coat so that the thermal expansion coefficient (TCE) of the metallic bond coat could be better matched to the ceramic overcoat into which the instrumentation was embedded. An optimized coating consisting of 20 wt% alumina and 80 wt% NiCoCrAlY yielded the greatest improvement in instrumentation lifetime and was based on an earlier combinatorial chemistry study. Electron microscopy revealed an ultafine dispersion of the metallic particles in a ceramic matrix that was extremely effective in reducing interfacial stress by reducing the thermal expansion mismatch between the NiCoCrAlY bond coat and the alumina overcoat. The peak to valley distance of the rough bond coat was also reduced using this approach and the lifetimes of thermal spray instrumentation were improved by more than 50% when cycled between room temperature and 1200°C. Copyright 2004 by ISA.
