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 th ermal stability. Fine polymeric powders are warmed up in oxy-acetylene flam e and sprayed onto a previously heated aluminium substrate. The degree of c rystallinity of PEEK coatings was investigated by differential scanning cal orimetry (DSC), according to the rate of cooling after the spraying process . FTIR-ATR revealed structural modifications, due to interactions between t he flame and the polymeric powders. Ultrasonic methods were developed, in p articular acoustic microscopy, to examine the variations of mechanical prop erties at the surface and the defects inside the material. Generally, flame -sprayed coatings contain a large amount of porosity. In addition, low-freq uency microechography, a non-destructive technique, is particularly suited to the observation of large defects (exceeding 50 microns) inside the polym eric materials.