Preparation of Mn doped Al2O3 heat-dissipating coatings on titanium alloy by cathodic plasma electrolytic deposition

Abstract

Mn-doped Al2O3 ceramic coatings were prepared on Ti alloys as heat-dissipating coatings by cathodic plasma electrolytic deposition (CPED) method. The composition, infrared spectral emissivity, thermal oxidation resistance, and thermal stability of the coatings were investigated, respectively. The XRD results suggest that the Mn-doped Al2O3 coatings are mainly consisted of α-Al2O3 and γ-Al2O3. The results of XPS spectra show that the Mn element is incorporated into the Al2O3 coating in the form of Mn4+. The emissivity test and cyclic oxidation test results indicate that the introduction of the Al2O3 coating can significantly improve the emissivity of the Ti alloy, and reduce the oxidation weight gain. In addition, the incorporation of Mn in the Al2O3 coatings can further enhance the emissivity value by 26.7% in the wave band 3–8 μm and 46.4% in the waveband of 8–20 μm, which has little impact on the oxidation resistance of Al2O3 coating after cyclic oxidation test for 200 h at 973 K.