Jiaping Han

Tinted plasma electrolytic oxidized (PEO) coatings have been widely applied on the surface of Ti alloys in aerospace field. In this study, a black PEO coating was successfully developed on TC4 alloy, incorporating MoSi₂ nanoparticles in situ within the coating matrix to enhance its corrosion resistance. The results indicated that the incorporation of MoSi₂ nanoparticles noticeably influence the coating morphology. The pore size decreased while coating thickness decreased from 15 μm to 12 μm. The incorporation of MoSi₂ enhanced the barrier property of the inner PEO layer, as well as decreased the surface roughness and increased the coating hardness, which improved the corrosion resistance. The i_corr dropped to 1.49 ± 0.58 × 10⁻⁷ A/cm² after the incorporation of the nanoparticles. A black PEO coating with particle addition was suggested for broader application on Ti alloys.

Wear resistance and optical properties are the key point for the application of titanium alloys as structural materials in the aerospace field. To enhance the wear resistance and optical properties of titanium alloys, a black plasma electrolytic oxidation (PEO) coating incorporating MoSi₂ nanoparticles was fabricated on the TC4 alloy via the PEO process, with the MoSi₂ nanoparticles being in situ doped into the coating. The doping of MoSi₂ nano-particles can effectively reduce the pore size of the PEO layer. The nPEO coating exhibited lower surface roughness than that of the PEO layer. The surface hardness of the nPEO coating increased to 42.5 HRC, significantly enhancing the wear resistance of the PEO layer (40.7 HRC). Furthermore, the PEO coatings exhibited better optical property compared to TC alloy, and the incorporation of MoSi₂ particles further improved the performance in most wavelength ranges. The infrared emissivity of the nPEO coating was 0.87, a dramatic increase from the 0.38 value of the TC4 alloy. This coating strategy effectively enhances the wear resistance and optical performance of TC4 alloy, which is critical for the surface design of titanium alloys used in aerospace applications.