Abstract: A method for optically detecting hot corrosion of a thermal barrier coating (TBC), comprising: providing a TBC which includes an indicator material which has an optical emission which is altered by corrosion of the coating; irradiating the TBC with an excitation beam of light; receiving an opticla emission from the TBC; obtaining a detection signal for the optical emission; and analysing the detection signal to identify one or more predeterminable spectral characteristics and evaluate the amount of corrosion of the TBC. Detection apparatus for optically detecting the corrosion of a thermal barrier coating with the mentioned method, and coating to be inspected by said apparatus and method.

Abstract: A coating material (20) for coating a machine component (10), especially a gas turbine or a part thereof, comprises a mixture of at least a refractory material and an indicator material having an optical emission (e.g. fluorescence) spectrum which varies in response to a physical parameter of the coated component. In a preferred embodiment, the coating consists of yttrium aluminium garnet (YAG) or yttrium stabilised zirconium. The dopant is preferably a rare earth metal, e.g. Eu, Tb, Dy.