Page 52 - MSAM-3-4

Materials Science in Additive Manufacturing Directed energy deposition

A

B

Figure 7. Microstructure and elemental distribution of (A) H-DED and (B) B-DED coating sub-surface. Red numbers indicate the points for chemical
composition analysis. Scale bars: 2.5 μm
Abbreviations: B-DED: Broad-beam laser-directed energy deposition; H-DED: High-speed directed energy deposition

Table 2. Chemical compositions of the H‑DED and B‑DED coatings that these oxides act as lubricants between the specimen
Coating Point Elements (wt.%) and the friction pair, reducing the friction coefficient and
Fe Cr C Ni Si Mo P S improving wear resistance. The average oxygen content
on the worn surfaces of the specimens is 9.91 wt.% (DI),
H-DED 1 62.2 22.6 6.4 7.0 0.8 0.8 0.1 0.1
26.4 wt.% (H-DED), and 13.2 wt.% (B-DED), which
2 66.2 18.9 3.9 8.9 1.1 0.9 0.1 0.0 corresponds with the wear resistance trend observed in
B-DED 3 64.4 22.3 7.1 4.2 0.7 1.2 0.1 0.0 Figure 9.
4 77.3 11.4 2.6 7.2 1.4 0.0 0.0 0.1 In Figure 10A and A , rows of grooves along the
1
2
Abbreviations: B-DED: Broad-beam laser-directed energy deposition; sliding direction can be observed, a typical characteristic of
H-DED: High-speed directed energy deposition.
abrasive wear. This is primarily due to spheroidal graphite
spalling during the wear process of the DI specimen,
in the DI specimen act as a third-body abrasive during forming a third body between the friction pair and the
wear, reducing the friction coefficient. 2,35 worn surface. Therefore, the wear mechanism of the DI
Figure 10 displays the localized wear morphology specimen is mainly characterized by three-body abrasive
and elemental distribution of the coatings and substrates. wear. The spalled graphite can absorb normal stress and
Prolonged and intense friction resulted in varying degrees grind the spalled material into finer debris, thereby
of oxidation on the surfaces of all specimens, as indicated reducing friction and improving wear resistance. However,
by the oxygen distribution maps. Studies 24,28 have reported the resulting voids are prone to stress concentration, leading

Volume 3 Issue 4 (2024) 7 doi: 10.36922/msam.4974