Testing of flame sprayed Al2O3 matrix coatings containing TiO2

The paper presents the results of the properties of flame sprayed ceramic coatings using oxide ceramic materials coating of a powdered aluininiuni oxide (Al₂O₃) matrix with 3% titanium oxide (TiO₂) applied to unalloyed S235JR grade structural steel. A primer consisting of a metallic Ni-Al-Mo based powder has been applied to plates with dimensions of 5X200X300 mm and front surfaces of ø40x50 mm cylinders. Flame spraying of primer coating was made using a RotoTec 80 torch, and an external coating was made with a CastoDyn DS 8000 torch. Evaluation of the coating properties was conducted using metallographic testing, phase composition research, measurement of microhardness, substrate coating adhesion (acc. to EN 582:1996 standard), erosion wear resistance (acc. to ASTM G76-95 standard), and abrasive wear resistance (acc. to ASTM G65 standard) and thermal impact. The testing performed has demonstrated that flame spraying with 97% Al₂O₃ powder containing 3% TiO₂ performed in a range of parameters allows for obtaining high-quality ceramic coatings with thickness up to ca. 500 μni on a steel base. Spray coating possesses a structure consisting mainly of aluminium oxide and a small amount of NiAl₁₀O₁₆ and NiAl₃₂O₄₉ phases. The bonding primer coat sprayed with the Ni-Al-Mo powder to the steel substrate and external coating sprayed with the 97%Al₂O₃ powder with 3% TiO₂ addition demonstrates mechanical bonding characteristics. The coating is characterized by a high adhesion to the base amounting to 6.5 MPa. Average hardness of the external coating is ca. 780 HV. The obtained coatings are characterized by high erosion and abrasive wear resistance and the resistance to effects of cyclic thermal shock.