Optimizing the plasma spray process parameters of yttria stabilized zirconia coatings using a uniform design of experiments

The plasma spray process parameters of yttria stabilized zirconia coatings with respect to deposition efficiency, porosity and microhardness were investigated using a uniform design of experiments. The measured deposition efficiency, porosity and microhardness of the coatings were regressed as the first- to third-order polynomial equations of five investigated process parameters, the arc current, argon flow rate, hydrogen flow rate, spray distance and powder feed rate, using stepwise regression analysis. It was found that the third-order regressed equations were the most appropriate to identify the influences of the investigated process parameters on the deposition efficiency, porosity and microhardness. Within the scope of the uniform design of experiments, the argon flow rate and the hydrogen flow rate appeared to be the most significant two parameters affecting the deposition efficiency, porosity and microhardness among the five investigated process parameters. Consequently, despite the fact that the regressed equations were different in terms of elements of the five investigated process parameters, the porosity decreased and microhardness increased with an increase in the deposition efficiency.