This paper presents the application of the surface response methodology and fractional factorial experiment in developing a robust partially stabilized zirconia (PSZ) coating in plasma spraying processes. In this study, a two-step experimental design with a nonlinear regression model is proposed. After conducting a series of initial experiments in a controlled environment, significant factors for plasma spraying processes are selected to construct an appropriate response surface model for developing a robust performance for plasma spraying processes. The experimental results show that using a quadric response surface model with the proposed two-step design strategy is a simple, effective and efficient approach. In the optimized model, several response plots were generated to examine parameter effects on the profile hardness. Optimization of the PSZ performances in a plasma spray process has been performed. (c) 2006 Elsevier B.V. All rights reserved.