Study on Microstructure and Properties of Aeronautical Nickel-Based Superalloy in Laser Directional Solidification

Abstract

FFor the directional solidification repair of blade damage in an aviation turbine, a directional-growth repair layer on the surface of a nickel-based superalloy was prepared using an Nd:YAG laser. The microstructure of the directional-growth repair layer was investigated using scanning electron microscopy and transmission electron microscopy. Its phase composition and corrosion resistance were also analyzed and tested. The results indicate that the grains in the repair zone solidified in the same direction as the substrate and formed continuous columnar crystals, which were arranged in an orderly manner. A small number of secondary dendritic cells were dispersed in the transverse direction of the columnar crystals. The phase composition was mainly composed of the α′-based phase, β-precipitated strengthening phase, MC carbide, and interdendritic α′/β eutectic phase. The corrosion kinetic curve of the repair zone changed linearly. The oxide film was uniform and dense, and was mainly composed of continuous granular oxide. The corrosion kinetic curve of the substrate conformed to the parabolic law. The oxide film was composed of loose and bulky granular grains, which were stacked in the shape of regular polyhedra and distributed in the form of an island.