Isothermal and Cyclic Oxidation Performance of Vertically Cracked and Columnar Thermal Barrier Coating Structures Produced Using Axial Suspension Plasma Spraying Process
Abstract:Oxidation performance of thermal barrier coatings (TBCs) deposited by the axial suspension plasma spraying (ASPS) method was evaluated under isothermal and cyclic conditions with a peak temperature of 1080 °C. The TBC systems are based on two nickel-based superalloy substrates (CMSX-4 and IN738LC), platinum aluminide bond coat (BC), and yttria-stabilized zirconia (8YSZ) top coat (TC) of either vertically cracked (VC) or columnar structure. Samples with IN738LC substrate exhibited longer isothermal oxidation li… Show more
“…And the Y–Al oxides could provide short-circuit paths for inward oxygen transportation and the oxide intrusions could be the preferable nucleation sites, accelerating the oxides scale growth [30]. The growth of the α-Al 2 O 3 phase resulted in the depletion of Al and reduced the ability of the coating to sustain the Al 2 O 3 -scale growth, which tends to generate Cr 2 O 3 with the absence of Al, causing the oxidation of Ni, Cr and Co [31,32]. Figure 4 The morphologies of the NiCoCrAlYTa coating after different oxidation time at 1050°C: (a,c) the surface and cross-section after 100 h oxidation, (b,d) the surface and cross-section after 200 h oxidation.…”
The NiCoCrAlYTa coating deposited on Ni-based superalloy using arc ion plating (AIP) technology was subjected to isothermal oxidation in air at 1050°C for up to 200 h. The microstructure, oxides scale thickness, growth stress and interface diffusion behaviour were characterized by using scanning electron microscopy, X-ray diffraction, electron probe microanalyser and photo-stimulated luminescence piezo-spectroscopy. The results revealed that the microstructure of oxides scale was predominantly composed of α-Al 2 O 3 with (Y, Ta)-rich oxides and Cr 2 O 3 irregularly distributed during the oxidation process. The oxides scale thickness of NiCoCrAlYTa coating conformed to parabolic law, which indicated the coating had good oxidation resistance. Also, the relationship between the thickness and growth stress, as well as the oxidation time, was studied based on the Clark oxidation theory and Wagner oxidation model, developing a methodology to measure the high-temperature stress in NiCoCrAlYTa coating. The theoretical calculation value of the stress was basically consistent with the value of the experiment, which could effectively predict the growth stress in the coating and help understand the failure mechanism of NiCoCrAlYTa coating during the service life. In the oxidation process, the interdiffusion behaviour occurred at the interface between the oxides scale and the NiCoCrAlYTa coating was also discussed. The diffusion coefficient of typical elements was calculated by using Boltzmann-Matano method, which was helpful to analyse the inner oxidation of the NiCoCrAlYTa coating, providing indepth understanding of the oxidation behaviour.
“…And the Y–Al oxides could provide short-circuit paths for inward oxygen transportation and the oxide intrusions could be the preferable nucleation sites, accelerating the oxides scale growth [30]. The growth of the α-Al 2 O 3 phase resulted in the depletion of Al and reduced the ability of the coating to sustain the Al 2 O 3 -scale growth, which tends to generate Cr 2 O 3 with the absence of Al, causing the oxidation of Ni, Cr and Co [31,32]. Figure 4 The morphologies of the NiCoCrAlYTa coating after different oxidation time at 1050°C: (a,c) the surface and cross-section after 100 h oxidation, (b,d) the surface and cross-section after 200 h oxidation.…”
The NiCoCrAlYTa coating deposited on Ni-based superalloy using arc ion plating (AIP) technology was subjected to isothermal oxidation in air at 1050°C for up to 200 h. The microstructure, oxides scale thickness, growth stress and interface diffusion behaviour were characterized by using scanning electron microscopy, X-ray diffraction, electron probe microanalyser and photo-stimulated luminescence piezo-spectroscopy. The results revealed that the microstructure of oxides scale was predominantly composed of α-Al 2 O 3 with (Y, Ta)-rich oxides and Cr 2 O 3 irregularly distributed during the oxidation process. The oxides scale thickness of NiCoCrAlYTa coating conformed to parabolic law, which indicated the coating had good oxidation resistance. Also, the relationship between the thickness and growth stress, as well as the oxidation time, was studied based on the Clark oxidation theory and Wagner oxidation model, developing a methodology to measure the high-temperature stress in NiCoCrAlYTa coating. The theoretical calculation value of the stress was basically consistent with the value of the experiment, which could effectively predict the growth stress in the coating and help understand the failure mechanism of NiCoCrAlYTa coating during the service life. In the oxidation process, the interdiffusion behaviour occurred at the interface between the oxides scale and the NiCoCrAlYTa coating was also discussed. The diffusion coefficient of typical elements was calculated by using Boltzmann-Matano method, which was helpful to analyse the inner oxidation of the NiCoCrAlYTa coating, providing indepth understanding of the oxidation behaviour.
The long-term durability is a considerable challenge for the use of thermal barrier coatings (TBCs). In order to solve this problem, introduction of yttriastabilized zirconia (YSZ) short fibers in functionally graded system is employed to strengthen the durability of TBCs. Four coatings are deposited on In738LC substrate by atmospheric plasma spray (APS). Thermal cycling behaviors and fiber toughening mechanisms of coatings are systematically studied. Result shows that the thermal cycling lifetime of graded TBCs with the addition of fibers can reach 406 AE 21 at 850 C, which increases by 60% compared to that of typical APS YSZ TBCs. Moreover, the improvement of lifetime mainly attributes to the fiber breakage, the fiber-matrix interface debonding, and the crack deflection.
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