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Microstructure of Nano-Y2O3/Cobalt Based Alloy Composite Coating by Laser Cladding
Pages: 683-686
Year: Issue:  5

Keyword:  metal materialsY2O3 nanocrystallinelaser claddingCo-based alloyequiaxed grainrare earths;
Abstract: Composite coatings made of nano-Y2O3/cobalt-based alloy and produced by crosscurrent CO2 laser on Ni-based superalloy are introduced. Cross-section or surface of the coatings was examined to reveal their microstructure using optical microscope,SEM,including EDS microanalysis,TEM and XRD. The results show that some equilibrium or non-equilibrium phases,such as γ-Co,Cr23C6,Y2O3 and ε-Co exist in the coatings. Fine and short dendritic microstructure and columnar to equiaxed transition (CET) occurred by adding nano-Y2O3 particles. With the increasing amount of nano-Y2O3(1%,mass fraction),fully equiaxed crystallization appeared. These are caused by nano-Y2O3 particles acting as new nucleation site and rapid solidification of the melt. The results also show that inhomogeneous dispersion of nano-Y2O3 results in the formation of ε-Co phase in the coatings. The sub-microstructure of the clad is stacking fault. The mechanism of the formation of equiaxed grains is also analyzed.
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