Single crystal twisting in additive manufacturing

Abstract Electron beam powder-bed fusion processing of metals (PBF-EB/M) enables additive manufacturing (AM) of Ni-base superalloys at high temperatures above 1000 °C. Previous studies demonstrated the successful processing of CMSX-4 single crystals (SX). The SX selection process is based on standard grain selection combined with a stress-induced twisting of columnar grains around the build direction. This mechanism steadily merges different grains of various secondary orientations into one SX. The necessary anisotropic stresses are induced by the applied hatching strategy. Thus, changing the hatching strategy and therefore the stress orientation should also change the SX orientation. This study demonstrates how an AM single crystal is twisted around the building direction when the hatching strategy and thus the stress field are slowly rotated around the building direction with increasing build height. Electron backscatter diffraction confirms a continuous rotation of the secondary orientation over the build height following the applied hatch rotation. Thus, the orientation of single crystals can be specifically changed in the additive manufacturing process.