An evaluation of plasma sprayed ceramic coatings by erosion, abrasion and bend testing

The mechanical properties of a series of plasma sprayed ceramic coatings made from alumina, chromia and alumina–titania precursor powders have been evaluated in particle erosion, two-body abrasion and bend testing. For the alumina coatings, both monocrystalline (sapphire) and polycrystalline alumina powders of varied grit sizes were used. Also, coatings of chromia and a mixture of alumina and titania were evaluated. The coatings were deposited with an axial injection spraying technique. Clear differences were found between the investigated coatings. Among the alumina coatings, those deposited from sapphire powders gave the best results in the wear tests. An addition of titania to alumina had a favourable effect in most tests. In abrasion, one chromia coating displayed a wear resistance comparable to the dense sintered alumina reference. The erosion rates were, however, several times higher for all sprayed coatings compared to the reference alumina.