The effect of metallic additives on the wear performance of the Cr2O3-based coatings

It has been acknowledged that damage tolerant thermally sprayed Cr₂O₃-coatings might be challenging to achieve. This has been associated to weak lamella bonding due to the high melting point of Cr₂O₃ and dusting followed by the strong tendency of chromium to evaporate. Attempts to improve the ductility or strain resistance of the coatings have been made by, e.g., blending another ceramic or metallic powder to the feedstock. This approach has not been advantageous for the fracture toughness determined by indentation. However, in macroscopic perspective, improved strain and damage tolerance could be necessary for a coating to withstand the requirement. Larger, ductile secondary phases might offer a viable solution to improve the performance of the Cr₂O₃-coatings for some critical applications. In our study, by using a novel powder modification approach, metallic additive (i.e. Ni, Co and Cr), have been implemented into the coating structure. APS and HVOF processes were used for the application of the coating. The wear resistance of the coatings was tested by rubber wheel abrasion, slurry and cavitation erosion, and sliding wear tests. The results showed that in many cases the metallic addition improves the performance of the coating compared to pure Cr₂O₃ and Cr₂O₃-25%TiO₂ –coatings.