Experimental design and performance analysis of alumina coatings deposited by a detonation spray process

The increasing demands for high-quality coatings has made it inevitable that the surface coating industry would put more effort into precisely controlling the coating process. Statistical design of experiments is an effective method for finding the optimum spray parameters to enhance thermal spray coating properties. In the present investigation, an attempt is made to produce high-quality alumina (Al₂O₃) coatings by optimizing the detonation spray process parameters following a (L16-2⁴) factorial design approach. The process parameters that were varied include the fuel ratio, carrier gas flow rate, frequency of detonations and spray distance. The coating characteristics were quantified with respect to roughness, hardness and porosity. The performance of the coatings was quantitively evaluated using erosion, abrasion and sliding wear testing. Through statistical analysis of the experimental results, performed by the ANOVA method, the significance of each process parameter together with an optimal variable combination was obtained for the desired coating attributes. Confirmation experiments were conducted to verify the optimal spray parameter combination, which clearly showed the possibility of producing high-quality Al₂O₃ coatings.