Microstructure and High-Temperature Oxidation Resistance of Cr-Al-Y Co-deposition Coating on TiAlNb9 Alloy Surface

Abstract:

To improve the high-temperature oxidation resistance of TiAlNb9 alloy, a Cr-Al-Y co-deposition coating was prepared on the alloy surface by the pack cementation method. The microstructure of the coating was analyzed by scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer, and the high-temperature oxidation properties of the substrate and coating at 1273 K were compared and studied. The results show that the Cr-Al-Y coating is about 30 μm in thickness, and it has a dense structure and good film-substrate bonding. The coating includes an outer layer composed of TiCr₂, TiCr, Ti₄Cr, and (Ti,Nb)Cr₄ phases as well as an inner layer composed of Ti₂Al, and Nb-rich γ-TiAl interdiffusion zone. The TiAlNb9 substrate forms an oxide layer composed of TiO₂ and Al₂O₃ at 1273 K. Due to its loose and porous structure, TiO₂ oxide film cannot effectively isolate the internal diffusion of element O, resulting in continuous oxidation damage to the substrate. The Cr-Al-Y co-deposition coating forms a dense Cr₂O₃ and Al₂O₃ oxide layer during oxidation, effectively preventing the internal diffusion of element O and significantly improving the high-temperature oxidation resistance of the substrate alloy.