Microstructure of ODS Superalloy Coating Produced by Laser Surface Cladding

Abstract:

Nano-Al2O3 dispersion strengthened Ni-based alloy coatings produced by crosscurrent CO2 laser on Ni-based superalloy are introduced. Cross-section of the coatings have been examined to reveal their microstructure, using optical microscope and SEM (including EDS microanalysis). The results show that rapid directional solidification of epitaxy is found at the interface where the growth direction is perpendicular to the bottom of melting pool. The size of columnar dendrite is decreased by adding Al2O3 nanocrystalline to the powder. A novel microstructure of equiaxed solidification has been observed with the increasing a mount of Al2O3 to 1% (in weight). Fine and equiaxed microstructure has been obtained for the nanocrystalline Al2O3 acting as new nucleation site of the melting pool.