PROCESS-IDENTIFICATION IN PLASMA SPRAYING THERMALLY SENSITIVE MATERIALS USING AN INFRARED THERMAL IMAGING-SYSTEM

Nowadays so called thermally sensitive materials are deposited by ther mal spray techniques. Due to the high temperature process an undesired alteration (evaporation, chemical decomposition! of the material coul d occur. Therefore, optimisation of the deposition based only on empir ical methods may be deremental with respect to the coating properties. This study shows the potential of an IR thermal imaging technique as a process control for evaluation and optimisation of the deposition th rough butter understanding of the thermal spray process. The spray tri als presented are based on preliminary examinations carried out with d iagnostic tools. Therefore it was possible to achieve defined air plas ma sprayed coatings of hydroxyapatite with different coating and compo nent properties. This is particularly of interest. since there exists only a standard for hydroxyapatite as starting material but not for pl asma sprayed coatings. Hence the coatings had either high or low conte nts of undesired phases, different degrees of cristallinity and bond s trengths-varying from 5 to 42 MPa. Besides the power levels and the wa y to obtain the power the carrier gas flow rate significantly influenc es the properties of the coatings.