Characterisation of plasma-sprayed coatings using NDE techniques

A round-robin test was implemented where nine European research institutions and universities applied different thermal, ultrasonic and magnetic methods for measuring the thickness of plasma-sprayed coatings. The coatings, which had thicknesses ranging from 50 to 500 microns, were applied on substrates of AISI 316, a standard industrial structural material, and on Armco-iron in order to have a material of known thermal properties. Destructive testing was performed after the other methods had been applied, resulting in detailed information on the coating thickness, rugosity, and uniformity. The results obtained with the applied methods on the two unknown samples for each substrate type agreed within 20% with the destructive testing data.