Improvement in the microstructure and property of plasma sprayed metallic, alloy and ceramic coatings by pre-/during-treatment of dry-ice blasting

Dry-ice blasting was introduced into plasma spray as substrate's under-cooling system to improve the microstructure and property of coatings. In this study, steel, CoNiCrAlY and Al2O3 coatings were deposited by plasma spray coupled with the pre-/during-treatment of dry-ice blasting. Moreover, the effect of dry-ice blasting as a pre-/during-treatment and only the during-treatment was examined to discover a better way to use dry-ice blasting during thermal spraying. It is revealed that a denser steel or CoNiCrAlY alloy coating with a lower content of oxide can be achieved with the application of dry-ice blasting during the plasma spraying. Such decrease of the oxide content is mainly attributed to the better cooling effect of dry-ice pellets. Interestingly, it is also found that the pre-treatment of dry-ice blasting on the substrate can help to get metallic, alloy and even ceramic coatings with improved adhesions. The adhesive strengths of steel, CoNiCrAlY and Al2O3 coatings were increased by 14%, 5% and 30%, respectively, compared with those of the coatings deposited with conventional air cooling. The cleaning effect of dry-ice blasting is responsible for the increase of the adhesive strength. Based on the present study, dry-ice blasting can be proposed as a pretreatment and cooling system during plasma spray. (C) 2012 Elsevier B.V. All rights reserved.