Microstructural characterization and fatigue performance of the recast material induced by laser manufacturing of a nickel-based superalloy

Laser manufacturing is widely used in modern industries for its high efficiency and accuracy. In the present work, the microstructures and mechanical properties of the laser-induced recast material on nickel-based superalloy Inconel 718 were systematically investigated. The mechanical property of the recast material was investigated with the help of the instrumented indentation technique improved by the reverse analysis algorithm. The yield strength and microhardness in the recast zone are much lower than that of the base material, which is attributed to the epitaxial growth of columnar grains and more to the decrease of strengthening phases γ^′ and γ^″. Whereas the recast-affected zone reveals higher yield strength for the growth of strengthening twins, the partial dissolution of the δ phase and cold work hardening manifested by higher misorientations. The high cycle fatigue performance of the recast material reduces significantly, which is caused by microstructural changes and defects including interval cavities and surface micro-cracks distributed in the recast zone.