Two-step plasma mediated synthesis of mullite and sillimanite powder and their suspensive spray coating on stainless steel

Abstract

We report a scalable two-step plasma mediated process for the synthesis of sillimanite and mullite spray grade powders and their coatings on stainless steel (SS) substrate. In the first step, spray grade sillimanite and mullite powders were prepared by thermal plasma processing followed by second step of plasma spray coating on SS. Xray diffraction has been used to study the phase formation and structural changes of powders before and after coating on SS. Grown-up stress and defects on the surface of the achieved coatings before and after mechanical tests was visualised by scanning electron microscopy. Mechanical hardness and wear tests were performed to compare the mechanical strength and applicability of these coatings in comparison to commercial powder coating. Further, electrochemical corrosion behaviour of these coatings in-comparison with commercial powder coating confirmed the potential of this two-step process and product for industrial scale-up.