Adhesion strength optimization of slurry sprayed mullite-based coating using Taguchi method

Abstract

Mullite-nickel-based coatings were deposited on low carbon steel by a relatively simple and low-cost surface deposition technique based on the slurry spray technique (SST) developed for environmental barrier coating applications. This paper reports the findings of an experimental investigation into the effects of SST process parameters in developing functionally graded mullite-nickel-based coating with adequate adhesion strength, analyzing the effect of TiO2 as liquid-phase sintering additive. The present study outlines the use of Taguchi’s experimental design based on L8 orthogonal array used to accommodate the factors selected as well as their interaction effects for performance optimization. Four key SST process parameters used for the study namely, sintering temperature, sintering time, percentage of additives, and stamping pressure have been optimized for the chosen response characteristic of adhesion strength. The significant effect of confounding variables in the prospective interactions has been investigated. Analytical results suggested that the factor sintering temperature has prominent effect on adhesion strength. It has also been found that the factor sintering temperature and sintering time have the most significant lower order interaction effect in the selected range of parameters. The developed coatings using SST demonstrate dense coating deposits with a satisfactory adhesion strength which is comparable with that produced from traditional techniques.