Improved oxidation resistance of CoNiCrAlTaHfY/Co coating on C/C composites by vapor phase surface alloying

A CoNiCrAlTaHfY/Co composite coating was prepared on the etched C/C composites by using duplex vapor phase surface alloying treatments, i.e., Co alloying and Co–Ni–Cr–Al–Ta–Hf–Y alloying. Microstructures and oxidation behavior of the coated C/C composites were analyzed by scanning electron microscop...

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Bibliographic Details
Published in:Journal of materials research 2020-03, Vol.35 (5), p.500-507
Main Authors: Guo, Qi, Meng, Tianxu, Ding, Wenqiang, Xi, Wen, Lin, Naiming, Yu, Shengwang, Liu, Xiaoping
Format: Article
Language:English
Subjects:
Alloying elements
Aluminum oxide
Applied and Technical Physics
Atoms & subatomic particles
Biomaterials
Buffer layers
Carbon fibers
Chemical vapor deposition
Coating
Cobalt
Composite materials
Cracks
Diffusion
Etching
High temperature
Honeycomb structures
Inorganic Chemistry
Materials Engineering
Materials research
Materials Science
Microwave plasmas
Mixed oxides
Morphology
Nanotechnology
Nickel
Oxidation
Oxidation resistance
Plasma etching
Stress concentration
Substrates
Surface alloying
Vapor phases
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Summary:A CoNiCrAlTaHfY/Co composite coating was prepared on the etched C/C composites by using duplex vapor phase surface alloying treatments, i.e., Co alloying and Co–Ni–Cr–Al–Ta–Hf–Y alloying. Microstructures and oxidation behavior of the coated C/C composites were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The result showed that the CoNiCrAlTaHfY/Co composite coating, 25 µm in thickness, was compact and composed of CrCoTa, AlCo 2 Ta, Al x Cr y , Al x Ni y , and Co. The coating adhesion can be enhanced by microwave plasma chemical vapor deposition etching of matrix surface and adding a Co intermediate layer between the CoNiCrAlTaHfY top layer and C/C composites substrate. The honeycomb structure after etching was helpful to alloying element absorb and diffuse into substrate surface, and the composite coating continuation was improved by the Co buffer layer. After exposing in air for 180 min at 1000 °C, the bulk C/C composites volatilized while the loss rate of coated C/C composites was 0.82%, showing an improved oxidation resistance. Mixed oxides mainly containing Al 2 O 3 and Cr 2 O 3 were formed in the composite coating surface and protected the C/C composites from oxidation in air.
ISSN:0884-2914
2044-5326
DOI:10.1557/jmr.2019.368