Microstructural evolution in ER70S-6 and 316L Steels under build orientations in LWAM

Laser Wire Additive Manufacturing (LWAM), a Directed Energy Deposition (DED) process, offers industrial advantages for manufacturing. However, the high thermal gradients produced due to the process may affect the mechanical performance of the deposited metal. This work continues previous work (Gomez-Lendinez et al., 2025) investigating how conditions and geometric orientation influence microstructure steel, comparing ER70S-6 carbon steel with stainless steel 316L.

Samples were produced using a Meltio M450. A comparison of Vickers microhardness tests and grain size analysis following ASTM E112 has been performed.

Results showed that heat dissipation led to significant differences: Horizontally built (XY) samples exhibited finer grains than vertically built (XZ) ones for the carbon steel, with microhardness following Hall–Petch trends. However, stainless steel shows no difference.

In conclusion, building orientation, which affects different thermal history, impacts the grain structure and mechanical behavior of LWAM-fabricated ER70S-6, but not for stainless stain 316L under optimal printing conditions. Effective thermal management strategies are therefore essential for achieving uniform mechanical properties and predicting microstructural evolution in wire-based additive manufacturing, depending on the materials used.

References:

Gomez-Lendinez, D. et al. Influence of Laser-Wire Metal Deposition Process Parameters on the Mechanical Properties and Microstructure of ER70S-6 Steel. J. Manuf. Mater. Process. 2025, 9, 157.