Microstructure and mechanical properties of laser-assisted epitaxial growth of nickel-based single crystal superalloys

The effects of process parameters on the microstructures and properties of the laser-assisted epitaxial growth layer are of great significance for the repair of nickel-based single-crystal blades. This work investigated the microstructures and properties of the epitaxial-growth laser-assisted nickel-based single-crystal superalloy. The effects of scanning path, laser power, scanning velocity and heat treatment on the microstructures and hardness of the laser-assisted epitaxial growth layer were explored. The microstructures of the epitaxial-growth samples are the same, starting from the bottom with a continuous columnar dendrite. The dendrites transform into isoaxial crystals when growing to a certain height. The scanning path, laser power, and scanning velocity mutually influence the sample's microstructures. The columnar crystal structure is very stable. Even the epitaxial-growth layer undergoes post-heat treatment, while the isoaxial crystal structure would be coarsened and the hardness decreases, but the subsequent aging treatment leads to an increase in hardness. These findings will greatly help improve the repair effect of single-crystal superalloys.