Effects of spray parameters on the adhesion between plasma-sprayed cast iron splat and aluminium substrate

For a thermally sprayed coating, a strong adhesion between the coating and the substrate is critical for its service performance. Furthermore, the adhesion between the coating and the substrate is mainly controlled by the splat-substrate adhesion. Therefore, enhancing the splat-substrate adhesion is important for the preparation and application of thermally sprayed coating. In the present work, individual cast iron splats were deposited on polished aluminium surfaces by atmospheric plasma spraying technique (APS) with varying plasma arc powers and spray distances. After spraying, the splat-substrate interfacial structure was examined by a field emission scanning electron microscope (FESEM). The effects of the arc power and spray distance on the morphology of the splats were studied. It was found that high arc power promoted splat-substrate adhesion by elevating the temperature and velocity of the impinging particles compared to low arc power. Moreover, a short spray distance promoted splat-substrate adhesion due to the heating of the substrate surface by the plasma jet and the high impinging velocity of the particles compared to a long spray distance.