Effect of alumina addition on the microstructure properties of plasma-sprayed zirconia-alumina coatings

Abstract

ZrO2/Al2O3 coatings with different amounts of Al2O3 were fabricated on the AISI 304 stainless steel surface using plasma spray process. Phase composition and microstructure of the coatings were characterised using X-ray diffraction and scanning electron microscopy. Lamellae and porous microstructure were obtained in the coatings. In addition, a small amount of unmelted particles, partially melted, and fully melted regions in microstructure of coatings were observed. With the increasing addition of Al2O3, a decrease in the pores was determined. The results indicated that the as-prepared ZrO2/Al2O3 based coatings were mainly composed of ZrO2, Al0.52Zr0.48O1.74, ZrTiO4, Al0.18Zr0.82O1.91, Al2O3, Al2Zr3, Al3Ti and Ti2O3 phases. The microhardness of the coating was as high as 1136 HV0.2, which was 4-5 times of the substrate.