Analysis of the high cracking resistance of a Co Ni superalloy during laser additive manufacturing.

A newly developed CoNi-based superalloy is demonstrated to be tolerant of a wide range of laser powder bed fusion print conditions, with limited defect content and high relative densities. These promising traits motivated investigation of the structural uniformity in samples printed at the upper end of the scan velocity processing window (>▪). A new misorientation metric, starting reference orientation deviation (SROD), was calculated from ▪-scale 3D microstructure information to examine structure evolution during epitaxial growth of columnar grains. Misorientations of >20° were observed within the large columnar grains that grew through multiple build layers. The SROD observations highlight the CoNi superalloy's ability to plastically deform to high levels, as evidenced by misorientation gradients, across the range of temperatures experienced in laser additive manufacturing. Misorientation gradients within the columnar grain structure are high relative to Ni base superalloys, allowing for strengthening with high volume fractions of L 1 2 precipitates. [ABSTRACT FROM AUTHOR]