Multilayer laser-assisted deposition on single crystal superalloy substrates

摘要

Laser powder deposition is a promising method for repairing single crystal Ni-based superalloy components used in the hot section of gas turbine engines. In this paper, recent results on multilayer deposits of NiCrAlY and Rene N4 on (100) single crystal substrates of SRR99- and CMSX-4 Ni-based superalloys are summarised. The deposited material presents a columnar dendritic microstructure consisting of arrays of similarly oriented dendrites forming a mosaic single crystal. Since solidification is epitaxial, the deposits inherit the orientation of the substrate. After aging, the γ'-Ni3Al precipitates do not present the cuboid shape required for high-temperature strength owing to chemical segregation within the dendrite arms resulting from solidification solute partition. Heat treatments capable of creating the proper particle microstructures were devised.