Damage mode analysis of MCrAlY overlay coatings subjected to isothermal stepwise tensile testing by usingin situvideo imaging and acoustic emission monitoring

Abstract

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.

Characterisation of the damaging micromechanisms in a pearlitic ductile cast iron and damage assessment by acoustic emission testing

“…Several studies used AE testing for the damage identification in various metals and alloys. However, very few studies applied AE testing for evaluation of damage in DCIs.…”

“…The evolution of the main features of the AEs (namely, AE features, Figure 2B) is potentially correlated to the damage, even though a more refined analysis typically allows a more robust assessment. 17,26,27 Several studies 21,25,[27][28][29][30] used AE testing for the damage identification in various metals and alloys. However, very few studies applied AE testing for evaluation of damage in DCIs.…”