Microstructure and hardness properties for laser powder directed energy deposition cladding of Inconel 718 on electron beam powder-bed fusion fabricated Inconel 625 substrates: As-built and post-process heat treated

Abstract

Laser powder directed energy deposition (LP-DED) additive manufacturing (AM) deposited Inconel 718 claddings (at laser power levels of 800, 1000, and 1200 W) onto Inconel 625 substrates fabricated by electron beam powder-bed fusion (EB-PBF). The cladding components were post-process heat treated for 1 h at temperatures of 1025 °C, 1175 °C, and 1250 °C. The microstructures and Vickers hardnesses were examined and compared for the as-built and heat treated cladding components. As-built claddings consisted of columnar dendrites and precipitate columns while the heat-treated microstructures consisted of varying degrees of recrystallization and grains containing {111} fcc annealing twins. The as-built cladding bond consisted of a 25–50 μm wide transition zone while the heat treated cladding bonds consisted primarily of linked grain boundaries sometimes alternating between the Inconel 718 alloy cladding and the Inconel 625 substrate. For the as-built components, the hardness increased from the Inconel 625 substrate to the Inconel 718 cladding. For the heat treated components, the hardness for the Inconel 718 cladding was lessened with increasing heat treatment temperature, but was overall similar to the Inconel 625 substrate.