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The presence of higher vol% of gamma prime (γ′) in Nickel-based superalloys is crucial for achieving superior high-temperature strength and creep resistance properties. While directed energy deposition (DED) offers promising solutions for repairing these alloys, they usually lack the precipitation of γ′ phases due to rapid solidification. This study investigates the precipitation behavior in DED-produced Inconel 100 (IN100) superalloy during as-deposited and post-heat treatment conditions, focusing on the evolution of γ′ morphology, size, volume fraction, and their correlation with mechanical properties. Results obtained from the combination of experimental studies and CALPHAD-based thermodynamic simulations in as-deposited conditions showed the presence of a γ matrix with MC carbides (rich in Ti and Mo) and eutectic γ/γ' phases in the interdendritic region, which are deleterious to mechanical properties. A subsequent post-heat treatment dissolved these intermetallic phases and improved the vol% of γ′. The solution heat treatments form the γ' in complex structures, following the Ostwald ripening and reverse coarsening effects, where γ' was observed in spherical (< 0.1 μm), cubic (0.1–0.5 μm), and octet (> 0.5 μm) shapes. One-step age hardening significantly increased the volume fraction of γ′, changing the γ′ morphology to cubes. The presence of γ′ was further enhanced during a 2-step age hardening with the precipitation of secondary γ′. The γ′ precipitation behavior was statistically quantified using advanced digital image analysis protocols and analyzed using Gaussian Mixture Models (GMM). The findings offer valuable insights into tailoring microstructure and enhancing precipitation strengthening in AM IN100, with potential benefits for high-temperature aerospace applications.
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Effect of Post Processing Heat Treatment Routes on Microstructure and Mechanical Property Evolution of Haynes 282 Ni-Based Superalloy Fabricated with Selective Laser Melting (SLM)
Selective laser melting (SLM) is one of the most widely used additive manufacturing technologies. Fabricating nickel-based superalloys with SLM has garnered significant interest from the industry and the research community alike due to the excellent high temperature properties and thermal stability exhibited by the alloys. Haynes-282 alloy, a γ′-phase strengthened Ni-based superalloy, has shown good high temperature mechanical properties comparable to alloys like R-41, Waspaloy, and 263 alloy but with better fabricability. A study and comparison of the effect of different heat-treatment routes on microstructure and mechanical property evolution of Haynes-282 fabricated with SLM is lacking in the literature. Hence, in this manuscript, a thorough investigation of microstructure and mechanical properties after a three-step heat treatment and hot isostatic pressing (HIP) has been conducted. In-situ heat-treatment experiments were conducted in a transmission electron microscopy (TEM) to study γ′ precipitate evolution. γ′ precipitation was found to start at 950 °C during in-situ heat-treatment. Insights from the in-situ heat-treatment were used to decide the aging heat-treatment for the alloy. The three-step heat-treatment was found to increase yield strength (YS) and ultimate tensile strength (UTS). HIP process enabled γ′ precipitation and recrystallization of grains of the as-printed samples in one single step.
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- Award ID(s):
- 2044352
- PAR ID:
- 10313338
- Date Published:
- Journal Name:
- Metals
- Volume:
- 10
- Issue:
- 5
- ISSN:
- 2075-4701
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/met10050629
