Fabrication and Property Evaluation of the Al2O3-TiO2 Composite Coatings Prepared by Plasma Spray

The Al2O3-13 wt.% TiO2 (AT13) composite coatings were prepared on Q235 steel by plasma spray technique. The spray parameters were designed by the orthogonal experiments, and the properties of the coating were evaluated. Results showed that with respect to the bond strength of the coating, the optimized spraying parameters were the plasma current of 530 A, Ar flow of 41 L/min, H2 flow of 10 L/min, and spray standoff distance of 100 mm. The plasma spray process led to the transition of α-Al2O3 to γ-Al2O3, resulting in the increase in the porosity of AT13 coating prepared at nonoptimized parameters. Meanwhile, the porosity and cracks were also increased due to the decrease in the Ar flow and the increase in spray standoff distance. The low porosity, a few cracks, and the uniformly dispersed TiO2 particles contributed the enhanced properties including mechanical and corrosion behaviors of the AT13 coating prepared at optimized parameters. The bond strength, microhardness, and thermal shock resistance of the AT13 coating could reach 25.01 MPa, 1000.6 HV0.5, and 40 times when the coating was prepared at optimized parameters, respectively. Especially, the static Icorr of the AT13 coating prepared at optimized parameters was two order of magnitude less than that of Q235 steel. In addition, the erosion weight loss of Q235 steel could be decreased about 30 times by the protection of the AT13 coating.