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Bond Coat

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Ping Xiao – 1st expert on this subject based on the ideXlab platform

  • superior oxidation and spallation resistant nicocraly Bond Coat via homogenizing the yttrium distribution
    Corrosion Science, 2019
    Co-Authors: Jie Lu, Chunshan Zhao, Xiaofeng Zhao, Ying Chen, Han Zhang, Ping Xiao

    Abstract:

    Abstract We present a novel approach to significantly improve the oxidation and spallation resistance of a NiCoCrAlY Bond Coat by homogenizing the yttrium distribution via powder milling and subsequent spark plasma sintering. The NiCoCrAlY Bond Coat fabricated by this method exhibits a much lower oxidation rate and a significantly better spallation resistance after isothermal oxidation at 1150 °C, compared with the counterpart fabricated from the un-milled powder. To understand the improvement in oxidation resistance, the microstructure of the Bond Coats, the chemistry and microstructure of the thermally grown oxides (TGOs), the TGO stresses and the interfacial chemistry are systemically investigated.

  • The oxidation performance of plasma-sprayed NiAl Bond Coat: Effect of Hf addition in Bond Coat and substrate
    Surface & Coatings Technology, 2018
    Co-Authors: Chunshan Zhao, Chengbo Xiao, Xiaofeng Zhao, Xin Wang, Ping Xiao

    Abstract:

    Abstract NiAl Bond Coats with and without Hf addition (0.1 at.%) were deposited on two types of superalloy substrates (i.e., DZ125L, no Hf, and DZ125, 0.51 at.% Hf) using plasma spraying technique, and isothermally oxidized at 1150 °C. It demonstrates that Hf addition in the Bond Coat is more effective than in the superalloy substrate for improving the Bond Coat oxidation resistance. In addition, though the substrate chemistry could affect the Bond Coat oxidation performance, this effect was very sensitive to the chemistry of the Bond Coat – obvious for the RE (reactive element)-free NiAl Bond Coat, but less obvious for the RE-containing Bond Coats (NiAlHf and NiCoCrAlY). Moreover, compared with the NiCoCrAlY Bond Coat, the NiAlHf Bond Coat showed significantly improved oxidation resistance, regardless of the substrate chemistry, suggesting that NiAlHf Bond Coat prepared by plasma spraying is a promising candidate for the thermal barrier Coating application.

  • high temperature stress and its influence on surface rumpling in nicocraly Bond Coat
    Acta Materialia, 2017
    Co-Authors: Lixia Yang, Xiaofeng Zhao, Ying Chen, Guangming Zhao, Ping Xiao

    Abstract:

    Abstract The objective of this work is to develop a methodology to measure the high temperature stress in the Bond Coat, and investigate its role on the surface rumpling. We first presented an analytical model to evaluate the high temperature stress using X-ray sin 2 Ψ technique coupling with the curvature measurement at room temperature. A typical NiCoCrAlY Bond Coat with a Hastelloy-X substrate was employed as a model sample. During exposure at 1150 °C, the Bond Coat was under tension at high temperature, increasing parabolically from 1.05 MPa after 12 h to 3.81 MPa after 120 h. To understand its effect on the surface rumpling, the Bond Coat surface roughness was recorded as a function of time, and compared with a bulk NiCoCrAlY alloy. A strong correlation between the Bond Coat stress and the surface roughness was identified. In addition, the origination of the Bond Coat stress and the rumpling mechanism were discussed. It was revealed that the high temperature stress in the Bond Coat was caused by the volume shrinkage from β-γ transformation, mainly due to the inter-diffusion. The grain sliding accompanied with diffusional creep in response to the Bond Coat stress controls the roughening.

Ung Yu Paik – 2nd expert on this subject based on the ideXlab platform

  • Thermal durability of thermal barrier Coatings with Bond Coat composition in cyclic thermal exposure
    Surface & Coatings Technology, 2015
    Co-Authors: Zhe Lu, Sang Won Myoung, Yeon-gil Jung, Ung Yu Paik

    Abstract:

    Abstract The effects of Bond Coat composition on the microstructure evolution and thermal durability of thermal barrier Coating (TBC) were investigated through cyclic thermal exposure. The microstructure of the Bond Coat was controlled using various feedstock powders, such as NiCrAlY, NiCoCrAlY, and CoNiCrAlY, which were Coated on the Ni-based substrate using a high-velocity oxy-fuel process. The top Coat was prepared with high purity feedstock powder (METCO 204 C-XCL) using an air plasma spray (APS) process. The thermal durability of the TBCs was evaluated through the cyclic thermal fatigue (CTF) and thermal shock (TS) tests, including the microstructure evolution, the thermally grown oxide (TGO) growth behavior, and thermomechanical properties. After the CTF and TS tests, the TBC with the Ni-based Bond Coat showed a longer lifetime performance and less degradation in hardness value than those with the Ni–Co- and Co–Ni-based Bond Coats. The results indicate that the Bond Coat composition produce an obvious effect on the thermomechanical properties of the TBC system. The relationship between Bond Coat composition and thermal durability is extensively discussed, based on the microstructure evolution and element diffusion behavior.

  • Control of Bond Coat microstructure in HVOF process for thermal barrier Coatings
    Surface & Coatings Technology, 2014
    Co-Authors: Sang Won Myoung, Zhe Lu, Yeon-gil Jung, Byung-koog Jang, Ung Yu Paik

    Abstract:

    Abstract The microstructure of Bond Coat was optimized by controlling Coating parameters, such as spray distances, the gas flow ratio of air/oxygen/hydrogen, gun speed, and step distance, in high-velocity oxy-fuel process, and the effects of Coating parameters on the microstructure and thermomechanical properties were investigated. When the spray distance to the substrate shortened, the microstructure became dense and the hardness values were increased. As the amount of hydrogen increased in the fixed gas flow ratio, defects such as global pores and oxides were increased and the hardness values were decreased, showing a similar trend in oxygen. The Bond Coat with the step distance of 8 mm showed a slightly higher hardness value than that with the step distance of 5 mm, indicating that the gun speed did not have much effect on the hardness value. However, in thermal diffusivity, the Bond Coat with the step distance of 5 mm showed lower values than that with the step distance of 8 mm. The optimum Coating parameters could be proposed in HVOF process.

  • Thermal fatigue behavior of air-plasma sprayed thermal barrier Coating with Bond Coat species in cyclic thermal exposure
    Materials, 2013
    Co-Authors: Zhe Lu, Sang Won Myoung, Yeon-gil Jung, Govindasamy Balakrishnan, Jeongseung Lee, Ung Yu Paik

    Abstract:

    The effects of the Bond Coat species on the delamination or fracture behavior in thermal barrier Coatings (TBCs) was investigated using the yclic thermal fatigue and thermal-shock tests. The interface microstructures of each TBC showed a good condition without cracking or delamination after flame thermal fatigue (FTF) for 1429 cycles. The TBC with the Bond Coat prepared by the air-plasma spray (APS) method showed a good condition at the interface between the top and Bond Coats after cyclic furnace thermal fatigue (CFTF) for 1429 cycles, whereas the TBCs with the Bond Coats prepared by the high-velocity oxygen fuel (HVOF) and low-pressure plasma spray (LPPS) methods showed a partial cracking (and/or delamination) and a delamination after 780 cycles, respectively. The TBCs with the Bond Coats prepared by the APS, HVOF and LPPS methods were fully delaminated (>50%) after 159, 36, and 46 cycles, respectively, during the thermal-shock tests. The TGO thickness in the TBCs was strongly dependent on the both exposure time and temperature difference tested. The hardness values were found to be increased only after the CFTF, and the TBC with the Bond Coat prepared by the APS showed the highest adhesive strength before and after the FTF.

Doris Sebold – 3rd expert on this subject based on the ideXlab platform

  • improvement of eb pvd thermal barrier Coatings by treatments of a vacuum plasma sprayed Bond Coat
    Surface & Coatings Technology, 2008
    Co-Authors: Uwe Schulz, O. Bernardi, Robert Vaßen, Andrea Ebachstahl, Doris Sebold

    Abstract:

    Abstract The lifetime of electron beam physical vapor deposited (EB-PVD) thermal barrier Coating (TBC) systems with conventional 7 YSZ ceramic top layers was investigated in 1 h thermal-cyclic testing at 1100 °C. The single crystal alloy CMSX-4 and the polycrystalline IN 100 alloy that had been Coated with a vacuum plasma-sprayed MCrAlY Bond Coat were chosen as substrate materials. A fully plasma-sprayed TBC system was studied as well. Several Bond Coat treatments such as smoothing, annealing in vacuum or air, and grit blasting were employed in order to study their effects on TBC life, and particularly the underlying mechanisms of thermally grown oxide (TGO) formation. Variations in TGO microstructure and especially occurrence or absence of the mixed zone have been correlated to the Bond Coat treatments. Spallation of the TBCs is mainly related to TGO formation that is influenced by the Bond Coat pre-treatment. The longest lifetime has been achieved by smoothing the Bond Coat prior to any heat treatment, followed by vacuum annealing prior to EB-PVD top Coat deposition. TBC lifetimes were longer on CMSX-4 than on IN100 substrates. The surface roughness of the Bond Coat did not influence TBC life much.

  • Improvement of EB-PVD thermal barrier Coatings by treatments of a vacuum plasma-sprayed Bond Coat
    Surface and Coatings Technology, 2008
    Co-Authors: Uwe Schulz, O. Bernardi, A. Ebach-Stahl, Robert Vaßen, Doris Sebold

    Abstract:

    The lifetime of electron beam physical vapor deposited (EB-PVD) thermal barrier Coating (TBC) systems with conventional 7 YSZ ceramic top layers was investigated in 1 h thermal-cyclic testing at 1100 ??C. The single crystal alloy CMSX-4 and the polycrystalline IN 100 alloy that had been Coated with a vacuum plasma-sprayed MCrAlY Bond Coat were chosen as substrate materials. A fully plasma-sprayed TBC system was studied as well. Several Bond Coat treatments such as smoothing, annealing in vacuum or air, and grit blasting were employed in order to study their effects on TBC life, and particularly the underlying mechanisms of thermally grown oxide (TGO) formation. Variations in TGO microstructure and especially occurrence or absence of the mixed zone have been correlated to the Bond Coat treatments. Spallation of the TBCs is mainly related to TGO formation that is influenced by the Bond Coat pre-treatment. The longest lifetime has been achieved by smoothing the Bond Coat prior to any heat treatment, followed by vacuum annealing prior to EB-PVD top Coat deposition. TBC lifetimes were longer on CMSX-4 than on IN100 substrates. The surface roughness of the Bond Coat did not influence TBC life much. ?? 2008 Elsevier B.V. All rights reserved.