Plasma sprayed ceramic coatings for electrical purposes-necessity of process control

Ceramic coatings with high electrical insulation capabilities can be sprayed onto metallic substrates by plasma spraying for insulation purposes, e.g. for corona rolls. However, the electrical and mechanical properties of such coatings severely depend on the spray conditions used during coating. This paper discusses the effects of spray conditions on coating properties and what parameters are essentially to be monitored for achieving high quality coatings. The paper is not confined to the classical machine parameter control techniques; however, it introduces recently developed diagnostic tools for the online monitoring of spray particle jet and substrate conditions.