Research On High-temperature Oxidation Property Of MCrALY Coatings On Nickel-base Superalloy K4104

Nickel-based superalloys have been widely used in aerospace field, especially in advanced gas turbines. These hot components are exposed to an extremely hostile enviroment. Thus a series of protective coatings are used for protecting hot section against oxidation corrosion. As a new type of Ni-based superalloy, the performance of K4104 were tested comprehensive, in order to applied better to resistance in aircraft engine turbin blade.The NiCrAlYSi diffusion coating was developed on Ni-based superalloy K4104 by Air-Ion Plating(AIP). It is oxielized in air at 900℃and 1100℃for time up to 300h.Its oxidation behavious including oxidation kinetic curves, surface and section topography, element diffusion law and the degradation of NiCrAlYSi coating is investigated by TGA, SEM, XRD and EDS.The result shows that the oxidation kinetic of alloy K4104 follows parabolic rate law under the 900℃for 300h, and linear equations under 1100℃for 300h. In the initial stage of high temperature oxidation, the sample's surface is covered by protective oxide film of Gr2O3. And a large number of NiCr2O4 and TiO2 generated with the processing of oxidation, the adhesivity and integrity of Cr2O3 was degenerate. As shown by section topography internal oxidation happened. Comparing with these two temperature, poor high temperature oxidation resistance, poor continuty of Cr2O3 oxidation film, serious oxide scale, internal oxidation and the generate of TiO2 under 1100℃circumstance.The alloy K4104 with NiCrAlYSi coating possesses more excellent oxidation resistant performance than the one without coating. The oxidation kinetic of alloy K4104 with coating followed parabollic rate law under both 900℃and 1100℃for 300h. On the surface of the alloy with coatings,an uninterruptedα-Al2O3 membrane was formed, Cr2O3 and NiCr2O4 were found at later stage oxidizing under 1100℃. The section topography showed that oxidation scales are composed of upper layerα-Al2O3, intermediate layerβ-NiAl, as well as inter diffusion zone with discrete o phase. The NiCrAlYSi coating was degenerated with the consume of Al element.β-NiAl phase was degenerated toγ'-Ni3Al andγ-Ni phase. In 900℃for 300h, theβ-NiAl phase was degenerated toγ'-Ni3Al phase with enough Al content to protect matrix. In 1100℃for 200h,β-NiAl phase was degenerated toγ-Ni phase,internal oxidation occured, coating damaged, alloy K4104 was no longer protected.