| The plasma spraying processing parameters of Al2O3+13%TiO2 (AT13) ceramic coating on AZ91D magnesium substrate were optimized by orthogonal experimental design in this paper. The microstructure and properties of plasma sprayed Al2O3+13%TiO2 coating were investigated by means of OM, SEM, EDX, XRD and so on.First of all, the influence of spraying distance, primary gas flow rate, deliver powder rate and spray power on the plasma spraying coating of Al2O3+13%TiO2 were investigated by orthogonal experiment design. The results show that the key parameters on the bonding strength are ranked as the sequence: deliver powder rate, spraying distance, spraying power and primary gas flow rate. According to this optimized parameters, the bonding strength of plasma spraying Al2O3+13%TiO2 coating was higher than any samples in orthogonal experiment. The fracture of coating occurred at the transition layer in which the elements content change obviously.The coatings are characteristic of lamellar microstructure and porosities, microcracks. The coalescent between coating and substrate is most of mechanical bond. Plasma sprayed Al2O3+13%TiO2 consists ofγ-Al2O3,α-Al2O3 and Al2TiO5. The microhardness of coating shows the scatter of distribution. The microhardness distribution of coating significantly conforms to normal and weibull distribution.Friction coefficient rises as the friction time increases when the experimental load is 10N and 20N. While the experimental load is 30N and the rotational speed is 100rpm, the friction coefficient reduces as the friction time increases. Friction coefficient rises as the friction time increases when the rotational speed is 100rpm, 150rpm, 200rpm. While the rotational speed is 200rpm and the load is 30N, the friction coefficient is lowest. The predominant wear mechanisms of coatings are spalling fatigue wear and adhensive wear. The thermal shock resistance experiment at the 350℃is performed in order to study resistance property to thermal shocks of plasma spraying AT13 ceramic coatings, and then the failure mechanisms of thermal shock resistance are analyzed and discussed. The results are indicated that the nature of the failure of coating is the fatigue under the thermal cycling stress, and the failure process consists mainly of cracks formation, cracks spread and the shedding of coatings.The highest variation of mass is unsprayed sample, next is unsealed and the sealed has the lowest variation of mass in the immersion experiment. The coating structure becomes loose after immersing. The etch pit of the surface of coating increases after corrosion. The corrosion current of coating dropped 3 magnitudes compared to magnesium alloy substrate.
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