Application of DOE and ANOVA in Optimization of HVOF Spraying Parameters in the Development of New Ti Coatings

Abstract

High velocity oxygen fuel (HVOF) thermal spray technique has been used to develop new Ti coatings on 1045 steel and 316L stainless steel for different applications. Optimization of the HVOF parameters requires numerous experiments to perform that can be reduced using the Taguchi Design of Experiment (DOE) methodology. By using DOE, it has been possible to identify the effects of the HVOF spraying parameters (spraying distance, number of layers, gun speed, powder feed rate, type of substrate and type of combustion) on the main characteristics of the coatings (porosity, thickness, hardness and adhesion). According to Taguchi method, the resulting orthogonal matrix corresponded to a L16 (44 × 22) matrix. Using this matrix, the number of experiments was reduced from 1024 to 16 and a first approximation of the best conditions for a real application was obtained. To evaluate the significant spraying variables, a statistical analysis of variance (ANOVA) was used. It has been determined that there is a relationship between coating characteristics and HVOF parameters. Also, the influence of the parameters on the characteristics and properties of the coatings (from high to low) is as follows: spraying distance, number of layers, gun speed, powder feed rate, type of substrate and mixture of gases used in the process.