Suspension Plasma Sprayed Chromia Coatings Ready for Industrial Applications

Chromia is one of the most used ceramic materials for thermally sprayed coatings in applications of wear protection. However, it is still challenging to produce dense coatings of high hardness both efficiently and reliably. The state of the art is atmospheric plasma spraying (APS) with powder feedstock material. In this study, high purity chromia in water based suspensions with 40 mass% solid content were used to apply dense coatings by a high power S-APS process Mettech Axial III. High productivity was achieved by increasing suspension feed rates and maintaining high deposition efficiency at spray distances similar to conventional APS. The coatings showed high deposition rates and hardness values about 1.600 HV0.3. Oscillating ball-on-flat sliding wear was tested as a measure of wear resistance and coefficient of friction. Thereby, the S-APS coatings of this study were compared to conventional APS chromia coatings and the low-carbon steel base material.