HVOF Coating Characterization by Acoustic Emission Using Four-Point Bending Test

Four-point bend test using acoustic emission (AE) was used to compare coating properties under mechanical solicitation, mainly the toughness and the spalling behaviour. Coatings are made from the same material; the 2005NS (WC-17Co), sprayed with an HVOF gun at various spray parameters. Coatings deposited on thin rectangular substrates were tested with the coating bent in tension and in compression. AE features like the event number, energy per event and cumulative energy were used to assess the damage in the coatings. The results are analyzed in relation with the coating microstructure.