Characterization of Adhesion Strength of HVOF Sprayed IN718 Coatings

Paper i proceeding, 2009

The tensile adhesion strength of thermally sprayed coating is conventionally evaluated via the ASTM C633-69 standard. The maximum measurable adhesion is then limited by the adhesion strength of the polymer media. High velocity oxy-fuel (HVOF) spraying can exhibit very high bonding strength and thus it is essential to develop an alternative method to evaluate coating adhesion strength. In this work a Modified Tensile Adhesion Test (MTAT) is proposed replacing gluing with induction brazing. The method was evaluated for HVOF sprayed Inconel 718 coatings deposited on Inconel 718 substrates. The effect of induction brazing process and the characteristics of the braze-coating interface was given particular interest. The results indicate that the method is superior to the ASTM C633-69 for characterisation of adhesion of coatings with high bond strength.