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Materials Science in Additive Manufacturing Inconel 718-CoCrMo bimetallic structures

powder (Stellite Coatings, Goshen, IN) was used with were taken for each point. For the compression tests, an
a particle size range of 50–100 μm. The bimetallic Instron servohydraulic compression tester was used to
structures were optimized until the part height was close determine the stress-strain curves for the longitudinal
to the theoretical height. The final parameters for each and transverse bimetallic samples and the base materials
sample are listed in Table 1. using a strain rate of 1.3 mm/min. For the oxidation tests, a
muffle furnace with no other additions was used to oxidize
2.2. Characterization of bimetallic samples
samples for 96 h at 800°C and then underwent the same
Bimetallic samples were cut in half and underwent a characterization process mentioned above.
typical grinding or polishing procedure. The samples
were then imaged using a field emission scanning electron 3. Results
microscope (FESEM, FEI-SIRION, Portland, OR) to 3.1. Microstructural variations
determine if any defects existed at the interface. Using the
energy dispersive spectroscopy (EDS; EDAX), elemental Figure 2 shows a stereoscope image of the bimetallic
maps were obtained to examine elemental distributions sample on a 316L substrate and the SEM/EDS analysis
at the interface. Vicker’s hardness testing (Penn Tool Co, of the interface. A small but distinct interface is formed
NJ) was performed along the interface and compared to between the CoCrMo and substrate. The same can be
the base materials’ hardness. At least 15 measurements observed between the Inconel 718 and CoCrMo junction,

Figure 1. Processing strategies of bimetallic structures of Inconel 718-CoCrMo using laser directed energy deposition process.

Table 1. Final DED build parameters for Inconel 718, CoCrMo, and bimetallic samples
Type of sample Inconel 718 CoCrMo Inconel 718 CoCrMo laser Inconel 718 CoCrMo Layer
scanning scanning speed laser power (W) power (W) flow rate flow rate height
speed (mm/min) (mm/s) (m m/s) (mm)
(mm/min)
Oxidation and Characterization Bimetallic 1200 1600 350 350 0.5 0.6 0.1
Inconel 718 Compression 1600 350 0.5 0.1
CoCrMo Compression 600 300 0.5 0.25
Transverse Bimetallic 600 1200 300 300 0.25 0.5 0.25
Longitudinal Bimetallic 800 1200 300 300 0.3 0.5 0.2
DED: Directed energy deposition

Volume 1 Issue 3 (2022) 3 https://doi.org/10.18063/msam.v1i3.18