Influence of Spraying Parameters on the Microstructure and Properties of Plasma-sprayed Al2O3/40%TiO2 Coating

Abstract

Abstract In this paper, the influences of parameters such as spraying voltage, spraying current, primary gas feed rate and spraying distance on the properties of plasma-sprayed Al2O3-40 wt.%TiO2 composite ceramic coating were studied by using orthogonal experimental design. The influence sequences of the parameters on the properties of plasma-sprayed Al2O3-40 wt.%TiO2 coating are: spraying distance, spraying voltage, spraying current, argon gas flow rate. The optimum parameters were determined: spraying distance 100 mm, spraying current 440 A, spraying voltage 120 V, and argon gas flow rate 3.0 m3/h. Scanning electronic microscope was used to observe the surface and cross-section morphologies of the Al2O3-40 wt.%TiO2 coating prepared by using the optimum parameters. The phase structure was analyzed by X ray diffraction. The through-thickness microhardness was measured by microhardness instrument. The bonding strength between the coating and substrate was determined by dual tensile test method. The porosity was measured by image analysis method. The results showed that the plasma-sprayed Al2O3-40 wt.%TiO2 composite ceramic coating has a dense structure with the porosity of 1.5%. In addition, the coating has typical layered structure. Al2O3-rich area and TiO2-rich area exhibiting different colors have homogeneous distribution and good combination. Due to the function of NiAl/AlSi bond coating, the bonding strength between the Al2O3- 40 wt.% TiO2 coating and substrate reaches 45 MPa. The coating is mainly composed of γ-Al2O3 metastable phase, α-Al2O3 stable phase, Ti8O15 and Al2TiO5.