Correlations of cracking with scan strategy and build geometry in electron beam powder bed additive manufacturing

Abstract

The extension of metal additive manufacturing (AM) to non-weldable Ni-based superalloys remains a challenge for the electron beam melting process. Various cracking mechanisms, including solidification, liquation, strain-age, and ductility dip cracking, make it difficult to fabricate traditionally non-weldable Ni-based superalloys using the AM process. Because airfoil geometries are highly complicated, the correspondingly complex thermal signatures lead to various types of cracking in geometries that are under severe mechanical restraints during the printing process. This work aims to understand the correlations between cracking, scan strategy, and part geometry in airfoil geometries. Crack locations were monitored via an in-situ near-infrared camera during printing. A part-scale finite element method (FEM) was used to reveal cracking mechanisms. New scan strategies that avoided cracking were utilized in an FEM simulation. The present work demonstrates the potential for scan strategy optimization to manipulate stress distribution and the resultant microstructure of parts for industrial applications.