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Microstructure of nanometer Al2O3dispersion strengthened Ni-based high-temperature protective coatings by laser cladding

Authors
Journal
Transactions of Nonferrous Metals Society of China
1003-6326
Publisher
Elsevier
Publication Date
Volume
19
Issue
3
Identifiers
DOI: 10.1016/s1003-6326(08)60317-9
Keywords
  • Functional Materials

Abstract

Abstract The nanometer Al 2O 3 dispersion strengthened NiCoCrAlY high-temperature protective coatings by crosscurrent CO 2 laser on Ni-based superalloy GH4033 were produced. Microscopic morphologies, phase constitutions of cladding coatings and distribution of nano-Al 2O 3 particles were examined using SEM and XRD. The results show that the interface grains, after adding proper nano-Al 2O 3, grow from epitaxial to non-epitaxial shape gradually, and the columnar dendrites become thinner and denser with cellular shape. Cracks in the substrate close to the interface are eliminated. Moreover, dispersive nano-Al 2O 3 particles mainly distribute around cellular substructure and on grain-boundaries, which prevents the diffusion of alloying elements and restrains the formation of new phase. There is a critical value of nano-Al 2O 3 addition, and the most suitable content of nano-Al 2O 3 is 1% (mass fraction) in this experimental conditions. The “nanometer effect” of nano-Al 2O 3 particles plays an important role in the improvement of coating microstructure.

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