DD10/NiCoCrAlYHf在1 150℃和1 200℃下的高温抗氧化性能研究OA

NiCoCrAlYHf coatings(HY5 coatings)are extensively applied on turbine blades to enhance the oxidation resistance of underlying superalloys.This work systematically investigates the high-temperature oxidation behavior and degradation mechanisms of HY5 coatings deposited on DD10,a third-generation single-crystal superalloy,substrates via multi-arc ion plating(AIP).The as-deposited coatings are subsequently subject to a vacuum annealing treatment at 1 050℃for 2 h to promote microstructural homogenization and relieve residual stresses.The chemical composition of the coatings is precisely measured as 54.5Ni-13.9Co-23.5Cr-7.5Al-0.7Hf with an average thickness of～25 µm.Microstructural analysis reveals that the annealed coatings primarily consist of β-NiAl and γ'-Ni3Al.Isothermal oxidation tests are conducted at 1 150℃and 1 200℃for 200 h,respectively.Then oxidation curves are obtained by plotting weight gains of coatings against oxidation time.The results reveal that a continuous,adherent,and protective α-Al2O3 scale,known as the thermally grown oxide(TGO),forms rapidly on the surface of both coatings during the initial oxidation stage.This is accompanied by a rapid weight gain within the first 15 h,amounting to～0.47 mg/cm2 at 1 150℃and～0.51 mg/cm2 at 1 200℃,which is directly attributable to the swift nucleation and lateral growth of the TGO.Subsequently,the oxidation rate decreases markedly,transitioning to parabolic kinetics,indicating that the dense TGO effectively serves as a diffusion barrier against oxygen ingress and cation outdiffusion.After 200 h of oxidation at 1 150℃,the coatings exhibit a total weight gain of～1.16 mg/cm2 and the TGO reaches a stable thickness of～8 µm,with no evidence of microcracking or spallation observed,demonstrating excellent scale adhesion.Nanoscale Y2Hf2O7 phases form within the TGO,which not only enhance the adhesion of the TGO but also reduce its growth rate.An interdiffusion zone(IDZ)of～80 µm forms beneath the coatings,characterized by gradually smoothed elemental concentration profiles.It confirms the significant interdiffusion of elements that act to mitigate the initial sharp compositional gradient between the substrates and the coatings.In contrast,the oxidation behavior at 1 200℃is more severe and leads to accelerated degradation.After 60 h of oxidation,the TGO thickness already reaches～7.5 µm with localized spallation,which is nearly comparable to the TGO thickness after 200 h of oxidation at 1 150℃;as the oxidation time extends to 100 h,non-protective,fast-growing mixed oxides of Co,Al,and Cr form on the surface and penetrate inward.EDS analysis indicates that the Al content in the coating matrix severely depletes to below 4%,compromising its ability to reform the protective Al2O3 scale.After 200 h of oxidation,the oxidation weight gain reaches～1.38 mg/cm2,and the destructive inward growth of mixed oxides exceeds a depth of 100 µm,penetrating to the alloy substrate.In summary,the HY5 coating exhibits excellent oxidation resistance at 1150℃,whereas at 1200℃,rapid TGO growth and premature spallation lead to a significant decline in its protective performance.