An important and often neglected factor in determining the final properties of a plasma sprayed deposit is its phase composition. It is well known that spraying of alumina results usually in the formation of phases other than the desired hard alpha-phase (corundum) unless a stabilizing admixture is added to the feedstock. In this work, chromia was used for stabilization and feedstocks with varying amounts of chromia were used to produced coatings by water spray plasma coating. Two types of feedstocks were used: fused/crushed feedstock and a mixture of alumina and chromia powders. The effect of the chromia content on phase composition, residual stresses, hardness, and wear abrasion of coatings was studied. Microanalysis indicates that a certain amount of chromium is transferred into alumina particles during the "in-flight" reaction of both powders in the plasma jet. Complex "alloy" oxides form where part of the aluminum is replaced by chromium and the alpha-phase is partially stabilized. However, any amount of chromia in coatings significantly changes the wear resistance and hardness even when the stabilization of corundum is only partial.

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