NiAlHf Coating on TiAl Substrate Prepared by EB-PVD

In order to improve the oxidation resistance of TiAl substrate at high temperatures, NiAlHf coating was prepared by electron beam physical vapor deposition (EB-PVD) on the TiAl substrate. According to the measured mass gain curves, the effect of NiAlHf coating on the oxidation behavior of TiAl substrate was studied at 900, 950 and 1000 degrees C. X-ray diffraction (XRD) was employed to identify the phases of the surfaces at different states. The XRD results show that beta-NiAl is formed after deposition and element Hf is found to be dissolved into it. A dense Al2O3 protection film is formed on the coating surface after 950 degrees C oxidation. Scanning electron morphology (SEM) with energy dispersive spectrum (EDS) was employed to characterize the morphology and element distribution at the cross-section and the surface. During oxidation, elements diffusion occurs at the interface between the substrate and the coating. With increasing of oxidation duration, the thickness of the coating decreases and the diffusion zone changes rapidly. Micro-hardness was used to characterize the coating toughness. Its micro-hardness is about HV7050 MPa. The results show that NiAlHf coating can improve the substrate oxidation resistance at high temperatures.