Strength of plasma sprayed turbine-blade coatings using an advanced spallation technique

We present an application of the spall technique for studying the strength, homogeneity, and adhesion of plasma sprayed coatings on a metal substrate. We used a flyer plate impact and a pulsed high-power proton beam to generate short, intense pressure pulses. To study adhesion it is necessary to provide a spall fracture at the interface. This was realized due to the bell-shaped power profile in the ion beam cross section. As a result, the spall fracture inside the samples occurred in tests with the ion beam, at different distances from the surface, including the interface between the coating and the substrate. Using a line-imaging laser-Doppler velocimeter, we were able to measure the free surface velocity histories for a range of load parameters in each experiment. The results of the measurements demonstrate the great influence of annealing on the homogeneity and strength of the coating and a lesser influence of the substrate temperature at coating on the adhesion. (C) 2001 American Institute of Physics.