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Cobalt superalloys such as Tribaloys are widely used in environments that involve high temperatures, corrosion, and wear degradation. Additive manufacturing (AM) processes have been investigated for fabricating Co-based alloys due to design flexibility and efficient materials usage. AM processes are suitable for reducing the manufacturing steps and subsequently reducing manufacturing costs by incorporating multi-materials. Laser directed energy deposition (laser DED) is a suitable AM process for fabricating Co-based alloys. T800 is one of the commercially available Tribaloys that is strengthened through Laves phases and of interest to diverse engineering fields. However, the high content of the Laves phase makes the alloy prone to brittle fracture. In this study, a Ni-20%Cr alloy was used to improve the fabricability of the T800 alloy via laser DED. Different mixture compositions (20%, 30%, 40% NiCr by weight) were investigated. The multi-material T800 + NiCr alloys were heat treated at two different temperatures. These alloy chemistries were characterized for their microstructural, phase, and mechanical properties in the as-fabricated and heat-treated conditions. SEM and XRD characterization indicated the stabilization of ductile phases and homogenization of the Laves phases after laser DED fabrication and heat treatment. In conclusion, the NiCr addition improved the fabricability and structural integrity of the T800 alloy.

Laser-directed Energy Deposition (laser-DED) is an additive manufacturing process where a 3D structure is fabricated layer-by-layer with powder that is directed and melted using a high power laser. The processing parameters of laser-DED have a strong influence on the microstructure of the samples that are fabricated. Due to a very high cooling rate, laser-DED produces some unique microstructures like columnar, dendritic grains, and macro-micro grains. The objective of this study is to understand how these microstructures will influence the ultrasonic properties of Inconel 718 (IN718). This work focuses on frequency-dependent parameters such as ultrasonic phase velocity, attenuation coefficient, backscatter and absorption, since they can be related to microstructural features spread over multiple wavelengths: grain size, grain orientation, phases, etc.

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