Investigation on Plasma Sprayed CoNiCrAlY-BN-Polyester Abradable Coating Consistency using In-flight Particle Diagnostics

The deposition of CoNiCrAlY-BN/Polyester powder by plasma spray often produces coatings exhibiting inconsistent properties. Consequently, a systematic investigation on the effect of variations in deposition and post treatment conditions was carried out. Coatings were produced by varying the stand-off distances and both primary and carrier gas flow rates while holding other spray conditions constant. The effect of these variations was correlated to both in-flight particle dynamics and coating properties. The former was characterized using optical diagnostic tools and the latter by SEM, XRD and Vickers and Rockwell hardness testing. The post heat treatment process needed to burn-out the polyester from the as sprayed coatings was also investigated using FTIR, SEM and DTA. The results showed that small variations in the spray conditions and post treatment can lead to significant changes in measured coating properties.