Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing

Abstract

Laser based powder bed fusion additive manufacturing offers the flexibility to incorporate standard and user-defined scan strategies in a layer or in between the layers for the customized fabrication of metallic components. In the present study, four different scan strategies and their impact on the development of microstructure, texture, and residual stresses in laser powder bed fusion additive manufacturing of a nickel-based superalloy Inconel 718 was investigated. Light microscopy, scanning electron microscopy combined with electron backscatter diffraction, and neutron diffraction were used as the characterization tools. Strong textures with epitaxially grown columnar grains were observed along the build direction for the two individual scan strategies. Patterns depicting the respective scan strategies were visible in the build plane, which dictated the microstructure development in the other planes. An alternating strategy combining the individual strategies in the successive layers and a 67° rotational strategy weakened the texture by forming finer microstructural features. Von Mises equivalent stress plots revealed lower stress values and gradients, which translates as lower distortions for the alternating and rotational strategies. Overall results confirmed the scope for manipulating the microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing by effectively controlling the scan strategies. • Laser powder bed fusion additive manufacturing (L-PBF AM) of a nickel-based superalloy Inconel 718 was performed. • Influence of four scan strategies X-, Y-, alternating (X-/Y-) and rotational (67º) was investigated. • X-/Y- strategies developed textured columnar grains and alternating/rotational strategies reduced the texture. • Fine microstructure with weak texture led to the least residual stress development in alternating/rotational strategies. • Scan strategies can be manipulated to control microstructure, texture and residual stresses during L-PBF AM.