Abstract
Superior wear resistance property of cast iron coatings is strongly linked to their microstructure. Graphite formation in plasma sprayed cast iron deposit is the main reason for this distinct phenomenon owing to its self-lubricant property. Since solidification rate affects graphite formation, optimization of spray conditions such as substrate temperature, chamber pressure, particle size and spray distance are required to slow down the solidification rate. The adhesion property of cast iron coating depends strongly on the adhesive strength between the first deposited layer and the substrate. It is important to improve the adhesive strength of splats by optimization of spray parameters. In this paper, cast iron splats were sprayed on aluminum substrate by plasma spray method using high Si and Al cast iron powders in Ar atmosphere. The effect of particle size and spray distance on splat microstructure (including graphite distribution) and its adhesive strength has been investigated. A correlation between microstructure and solidification rate was also introduced. Spraying by using large particle size leads to an increase in the number fraction of disk splats and a decrease in the splat’s adhesive strength. In contrast, the number fraction of star-shaped splats and their adhesive strength increase by spraying using small particle size. Longer spray distances lead to a decrease in number fraction of disk splats and their adhesive strength. The rear-side observation of cast iron splats sprayed with different spray distances show no distinct difference.
