1-D MODELING OF COATING FORMATION UNDER PLASMA SPRAYING CONDITIONS: SPLAT COOLING AND LAYERING

In the plasma spray process, powder particles are accelerated and heated by a plasma jet and impact at high velocity on the part to be covered. Upon impact, they flatten and solidify at high cooling rate (10⁶ -10⁸ K/s), most of the thermal energy of the impinging particles being transferred by conduction to the substrate and the previously deposited layers.

The formation of the coating is governed by various time scales ranging between microseconds (particle flattening and splat solidification) and seconds (time between two passages of the gun by the same location). This large range makes the deposit process difficult to simulate. However, such simulations can help to have a better understanding of coating building and, therefore, a better control of coating quality.

This paper presents a numerical simulation of the cooling and layering of splats. 1-D approach is used. It takes into account the quality of contact between splats or between coating layers. The effect of particle and process parameters on splat cooling rate, layer cooling and temperature history are investigated.