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The study results phase composition of the coatings showed that the coatings were composed γ-Al2O3 and Al2TiO5 phase. The compounds AlPO4 and Al(PO3)3 were found in the coating sealed with aluminum phosphate. The coatings sealed with aluminum phosphate containing Al2O3 nanoparticles have lower porosity density, higher hardness and higher wear resistance than the coating sealed with aluminum phosphate uncontain Al2O3 nanoparticles and the unsealed coating. | Vietnam Journal of Science and Technology 55 (6) (2017) 698-705 DOI: 10.15625/2525-2518/55/6/9026 EFFECTS OF ALUMINUM PHOSPHATE SEALANT CONTAINING Al2O3 NANOPARTICLES ON THE HARDNESS AND WEAR RESISTANCE OF THE Al2O3-TiO2 PLASMA SPRAYED COATING Pham Thi Ha1, *, Pham Thi Ly1, Nguyen Van Tuan1, Vo An Quan1, Le Thu Quy2 1 Institute for Tropical Technology, VAST, 18, Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam 2 National Key Laboratory for Welding and Surface Treatment Technologies, NARIME 4 Pham Van Dong, Cau Giay, Ha Noi, Viet Nam * Email: hapham205@gmail.com Received: 16 December 2016 ; Accepted for publication: 8 October 2017 Abstract. In the present study, Al2O3-40 wt.% TiO2 composite coatings were fabricated on medium carbon steel substrate by plasma spraying technique. The coatings were sealed with aluminum phosphate solution containing 5 wt.% Al2O3 nanoparticles and then heat treated at 400 oC. The phase composition, structure morphology, microhardness and wear resistance of the coating were studied. The study results phase composition of the coatings showed that the coatings were composed γ-Al2O3 and Al2TiO5 phase. The compounds AlPO4 and Al(PO3)3 were found in the coating sealed with aluminum phosphate. The coatings sealed with aluminum phosphate containing Al2O3 nanoparticles have lower porosity density, higher hardness and higher wear resistance than the coating sealed with aluminum phosphate uncontain Al2O3 nanoparticles and the unsealed coating. Keywords: Al2O3-TiO2 coating, aluminum phosphate, plasma spraying, Al2O3 nanoparticles. 1. INTRODUCTION Plasma spraying is a versatile technology to produce protective coatings for facilities in extensive application. Many studies indicate that Al2O3-TiO2 plasma sprayed coatings have good corrosion, wear and erosion resistance [1 - 11]. However, owing to their lamellar structure and rapid solidification, plasma sprayed coating usually have plenty of cracks and voids. These structural defects provide paths for
