A B S T R A C TThe mechanical performance of gas turbine material systems consisting of a Ni-base superalloy substrate with three different MCrAlY overlay coatings with various Al contents was assessed, close to service temperature spectrum, by means of stepwise tensile tests. Furthermore, acoustic emission (AE) activity was monitored during the tensile testing. Tensile tests were performed for all three types of coated systems at four different temperatures (300, 500, 700 and 900 • C). The AE data were analysed by means of a standardized k-means algorithm with respect to nine parameters (such as amplitude, number of counts, duration, rise time, energy, etc.). In conjunction with in situ video imaging of the specimen surface and postmortem microstructural analysis of the samples, the classification of AE data has provided a means for damage identification and performance assessment of the substrate-coating material systems.