Optimization of the Si3N4 coating formation through plasma spraying on Inconel 738

In the present study, the deposition of silicon nitride (Si3N4) coating on Inconel 738 through plasma spray has been investigated. For producing the Si3N4 coating, different times (6, 8 and 10 s), different distances of the plasma spray torch from the substrate (30, 35 and 40 mm) and different currents for plasma spraying (3000, 3250 and 3500 A) were employed. For the characterisation of the coatings, SEM (thickness), XRD, micro-hardness and adhesion of the samples were measured. The coatings' surface morphology was investigated through SEM. Based on the experimental results, by using a spraying time of 10 s, a distance of the torch of 40 mm and a current of 3500 A, high microhardness and adhesion of the coatings are obtained. On the other hand, the thickness of the coating increased by reducing the distance and increasing spray time and current.