Non Destructive Resting of the Coating-Subsrate Interface of Thermally-Sprayed Industrial Parts Non Destructive Testing of the Coating-Substrate Interface of Thermally-Sprayed Industrial Parts

Abstract

The present work deals with the application to actual in industrial conditions of the promising results of the study on adhesion, as presented at the previous edition of ITSC’2004 in Osaka, Japan. These industrial parts were typical of those produced in workshops for aircraft-aerospace, petro-chemical, printing works industries etc…. Thermal spray processing of industrial parts tested in this study are numerous, primarily air plasma spraying (APS), HVOF and conventional flame spray with or without remelting. Ultrasonic NDT facilities are now installed in an actual industrial workshop and show the reliability of the testing method and related results. For every tested part, digital ultrasonic testing was carried out to be compared to results from conventional adhesion tests according to EN 582 standard. U.T. results were quite in keeping with those from EN 582 testing. However, in addition, ultrasonic testing exhibited the any heterogeneity when existing, (local weak zones) at the coating-substrate interface. This resulted in easy discriminating of adhesive areas from cohesive areas. Results of this work obtained in a real workshop environment leaves promising expectations for ultrasonic testing to meet results from conventional EN 582 adhesion testing when applied to industrially-produced parts. Ultrasonic testing results in a low-cost NDT method which should compete with current high-cost control. Moreover, ultrasonic NDT looks more reliable in so far as the whole part can be controlled due to scanning of the whole surface.