Influence of particle size and spray parameters on structural, mechanical and electrical insulation properties of alumina coatings by atmospheric plasma spraying

Aluminum oxide coatings by atmospheric plasma spraying (APS) have being widely applied in various industries historically because of their excellent properties on electrical insulation, high wear resistance, high heat conduction, and so on. They can be coated onto a wide variety of substrates almost without any limitation such as wide area, relatively complexed shape with desired thickness around a few hundred micron. However, the properties of APS alumina are generally inferior to those of sintered bulk due to pores, micro-cracks, metastable gamma phase, residual stress, and imperfect bonding between particles, which should be improved to catch up with advanced demand technically from many industries.

In this study, influence of particle size and spray parameters on structural, mechanical and electrical insulation properties has been studied for alumina coatings by atmospheric plasma spraying. It has been found that finer particles are effective for coating formation at high velocity plasma with TriplexPro-210^TM, which contributes to obtain superior insulation properties. On the other hand, standard particles, standard plasma conditions of lower plasma velocity and traditional plasma gun are difficult to have better coatings with high electrical insulation. Crystal structures of the coatings will be also investigated to study the factors affecting the properties comprehensively.