Abstract:The work aims to prepare the mullite/Mo coating on aluminum alloy surface, and reveal the relationship between microstructure, mechanical properties and thermal protection. The refractory metal Mo bonding coating and mullite ceramic top coating were prepared by atmospheric plasma spray (APS) technology. The microstructure, phase composition and element distribution of the coating were analyzed by SEM, XRD, EDS and so on. The thermal protection characteristics, including thermal expansion coefficient, thermal conductivity, thermal shock performance, were investigated. At the same time, the failure mechanism was revealed, as well. The elements and phases of the mullite/Mo coating prepared by APS technology are evenly distributed. The microhardness of mullite coating is about 503.8±99.68 HV300g, and its bonding strength is about 32.23±2.55 MPa. The thermal conductivity of the mullite coating is 1.52 W/m?K at room temperature, the infrared emissivity is about 0.875, and the sunlight absorption ratio is 0.313. The mullite/Mo coating could undergo 15 times thermal shocks at 400 ℃. In total, the mullite/Mo coating is uniform and dense, and well bonds on aluminum alloy. What’s more, the mullite coating exhibits better mechanical properties, and has high matching degree with refractory metal Mo bonding layer. Thus, the mullite/Mo coating which can play an excellent thermal protection effect on metal hot-parts, and thus promote the safe and stable operation of space vehicles.