Influence of Metal Bond Coat Thickness on Adhesion Strength of APS Ceramic Coatings

Influence of Metal Bond Coat Thickness on Adhesion Strength of APS Ceramic Coatings. Repair of ball valves typically requires: GTAW substrate welding, surface grinding, and applying (APS) ceramic coating. An alternative repair method is to machine the ball undersize, put a thicker metal bond coat under the Ceramic coating to re-establish original dimensions. This study was performed to determine if ASTM C633 adhesion strength of an APS Ceramic coating was dependent upon thickness limit of HVOF applied NiCrMo (Hastelloy) bond coating. 8 thicknesses of NiCrMo were applied to three substrates: Titanium G12, Inconel 625, and 2507 Duplex SS. 3 APS Ceramics: Cr2O3, Cr203-Al2O3, and TiO2, were applied 0.015in of thickness over the NiCrMo coated samples. Metal bond coat thicknesses were: 0.0015in, 0.005in, 0.015in, 0.030in, 0.045in, 0.060in, 0.075in, and 0.090in. Coatings were evaluated by: ASTM C633 adhesion strength testing, percent porosity (ASTM E2109 Method B), and Vickers hardness testing (ASTM E384).