Characterization of flame‐sprayed PEEK coatings by FTIR‐ATR, DSC and acoustic microscopy

Poly (aryl ether ether ketone) (PEEK) was used as a flame-sprayed coating, due to its good mechanical properties, low friction coefficient and high thermal stability. Fine polymeric powders are warmed up in oxyacetylene flame and sprayed onto a previously heated aluminium substrate. The degree of crystallinity of PEEK coatings was investigated by differential scanning calorimetry (DSC), according to the rate of cooling after the spraying process. FTIR-ATR revealed structural modifications, due to interactions between the flame and the polymeric powders. Ultrasonic methods were developed, in particular acoustic microscopy, to examine the variations of mechanical properties at the surface and the defects inside the material. Generally, flame-sprayed coatings contain a large amount of porosity. In addition, low-frequency microechography, a non-destructive technique, is particularly suited to the observation of large defects (exceeding 50 microns) inside the polymeric materials.