3D printer manufacturer Digital Metal® continues to add new materials to its binder jetting system. Its latest superalloy, DM 718, is an alloy designed to withstand extreme temperatures and corrosive environments, while exhibiting excellent weldability.
DM 718 is equivalent to UNS N07718, more widely known as Inconel® alloy 718, an alloy commonly used in applications that require high strength and corrosion resistance at extreme temperatures. Typical applications include: gas turbines, jet engines, rocket engines, turbo pumps, and pressure tanks.
DM 718 is a nickel-chromium-based precipitation-hardening superalloy. It offers high strength, as well as creep and corrosion resistance, in cryogenic and elevated temperatures, up to about 650°C. Versatile and high-performing, this alloy composition is the most used nickel-chromium superalloy in metal additive manufacturing, in addition to being one of the most commonly used superalloys, overall.
The material properties of DM 718 are quite satisfactory in the as-sintered state; however, post-sintering heat treatments are required to take full advantage of its composition. The alloy can be strengthened using industry-standard treatments, consisting of solution annealing and quenching, followed by aging steps.
Welding behaviour stands out
Compared with some other superalloys that have similar high-temperature strength characteristics, a key benefit of alloy 718 is its welding behaviour – particularly its resistance to post-weld cracking.
The alloy has a slow response to age-hardening and is primarily strengthened by gamma double prime (γ’’) precipitates. This combination offers improved weldability over high gamma prime (γ’) alloys, such as DM 247. However, the γ’’ phase begins to dissolve at temperatures above 650°C, the material then loses some of its strength. Meanwhile, the γ’ phase remains stable and continue to provide strength to slightly higher temperatures. Though in general, alloys with high levels of γ’ cannot be welded.
In Q4, 2022, Digital Metal will begin offering print services for DM 718 components in the as-sintered state, as well as collaborating with external partners to offer components in various other heat-treated states. This alloy is also available as a turnkey solution (including consumables and process parameters), for customers who are already using Digital Metal’s systems to process other steels and superalloys.
An expanding material portfolio
DM 718 and DM 4140 are the latest additions to the company’s binder jetting system. Other materials in the range are pure copper DM Cu, stainless steel 316L and 17-4PH, tool steel DM D2, superalloys DM 625 (equivalent to Inconel 625) and DM 247 (equivalent to MAR M247), and Titanium Ti6Al4V.
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