On the Deformation Behavior of Metastable CrMnNi Steels Processed by Directed Energy Deposition in Different Temperature Regimes

Directed energy deposition (DED) as an additive manufacturing (AM) technique with its high productivity is a promising technology with respect to rapid repair applications. Although process characteristics like the layer-wise built-up are similar in all AM processes, the microstructure and resulting properties are unique for all primary shaping technologies. In the present study, metastable CrMnNi steels with varying chemical compositions and a concomitantly altered stacking fault energy are processed via DED and afterwards tested via tensile tests at different temperatures. Depending on the specific stacking fault energy of the alloy and deformation temperature, the microstructure is dominated either by martensitic phase transformation, twinning, or slip. The resulting characteristic curves are compared to results from literature focusing on other primary shaping technologies such as laser-based powder bed fusion of metals and casting. Depending on the manufacturing technology, the shape of the stress–strain curves varies. This can be rationalized based on initial dislocation densities as well as chemical homogeneity. The prevailing microstructural features influence the work hardening behavior as well as the homogeneity of deformation due to locally varying chemistry and stacking fault energy.