Page 49 - MSAM-3-4

Materials Science in Additive Manufacturing Directed energy deposition

A B

Figure 2. Localized surface morphology of (A) high-speed directed energy deposition (H-DED) and (B) broad-beam laser-directed energy deposition
(B-DED). Scale bars: 500 μm

A B

C D

Figure 3. Cross-sectional macroscopic morphology (A and C) and binding zone microstructure (B and D) of the coatings through various directed energy
deposition (DED) technology. Scale bars: 1000 μm (A and C); 40 μm (B and D)
Abbreviations: B-DED: Broad-beam laser-directed energy deposition; H-DED: High-speed directed energy deposition
stacked structure with higher roughness, whereas the during the solidification of the molten pool, the carbide
B-DED coating surface is smoother. Although the shape with the highest affinity for carbon forms first. The Gibbs
of the binding line varies, both coatings exhibit strong free energy of M C remains lower than that of carbides,
23
6
metallurgical bonding with the substrate (Figure 3B and D). such as M C and M C over a wide temperature range,
3
7
2
3
As the H-DED coating has a smaller melt pool diameter, it causing M C to precipitate first. However, the overall
6
23
has a more curved binding line than the B-DED coating. carbide content in the deposited coating is low, possibly
indicating insufficient carbon atoms in the molten pool
3.2. X-ray diffraction of the coatings to form other carbides. As key hardening phases, these
Figure 4A displays the XRD patterns of B-DED, H-DED, carbides feature complex structures, high melting points,
and the deposition powder. The powder and coatings and hardness, enhancing the coating’s wear resistance and
primarily consist of a face-centered cubic austenitic phase hardness. 23,25
(γ-Fe), along with a small amount of carbides. The γ-Fe The different DED process influences the preferred
phase corresponds to the (111), (200), (220), and (311) orientation of the surface grains but does not change the
crystal faces. The carbides are present in the form of phase composition of the coating. The peak shape and
interstitial phases, mainly M C (M = Fe, Cr). Given the position of the H-DED coating are similar to those of the
23
6
similar lattice and electronic structures of Fe, Cr, and Fe deposition powder, but the intensity of the diffraction
atoms, some Cr atoms in Cr C can be easily replaced, peaks has increased, particularly for the (111) crystal
23
6
forming M C -type carbides. Research revealed that face, where both the intensity and the full width at half
25
6
23
Volume 3 Issue 4 (2024) 4 doi: 10.36922/msam.4974