In this work, the effect of three principal and independent parameters of Atmospheric Plasma Spray on the properties of coatings deposited using mixtures of commercial powders of titanium dioxide (TiO2) and chromium oxide (Cr2O3) was studied. The results of this work are used for special applications on turbomachinery components such as wear protection in sliding seals and in steam valves for turbines, chemical protection for centrifugal compressor members, and special seal applications.
The design of experiments (DoE) technique has proved to be very useful to study the influence factors and optimization. Pierlot et al.  demonstrated that the application of the Hadamard and two factorial design techniques are useful for the optimization of thermal spray processes. An example of the application of the DoE is the one mentioned by Murugan et al. . In their work, a factorial design was used to study the interactions between gas flow, oxygen flow, powder rate and spray distance on the percentage of porosity and hardness of TiO2 - Cr2O3 composite coatings generated by High Velocity Oxy-Fuel.
The ½ fractional two-level factorial DoE technique was used to analyze and optimize the Atmospheric Plasma Spray process parameters. In the current research, experiments were conducted varying the deposition velocity, gas flow and stand-off distance. The effect of these process variables were evaluated by thickness, hardness and microstructure analysis. In this study, an empirical relationship between process variables and response parameters was developed. The entire relationship was made using the results of the DoE.