High Temperature Oxidation-Resistance of GH4169 Alloy Surface Modified with NiAl Ion-Plated Coatings

The surfaces of GH4169 alloy,an important aero-engine material,were modified with NiAl coatings deposited by ion plating.Oxidized at 1100℃,the surface microstructures,phase structures and oxidation behavior of the NiAl-coating were characterized with X-ray diffraction,energy dispersive spectroscopy and scanning electron microscopy.The results show that the NiAl coating significantly increased the high temperature oxidation resistance.After annealing and ageing,β-phase grains dominated the compact 15 μm thick NiAl coatings with strong interfacial adhesion.In oxidation at 1100℃,a dense and compact Al₂O₃,top-layer formed in the initial stage,effectively prevented further oxidation and consumption of Al;later on,α-phased Al₂O₃ and γ-phased Ni₃Al coexisted in the NiAl coating;as the oxidation time increased,the spinel structured grains formed,possibly resulting in vanishing of β-phased NiAl diffraction peak and weakening of the Al₂O₃-layer protection.