Description

Additively Manufactured Ferritic Steel with Enhanced High-Temperature Performance Grade 91 steel is one of the most widely used structural metals in power plants and candidate for advanced nuclear reactors, but it loses much of its strength when operating temperatures climb above 500°C. Researchers at Los Alamos National Laboratory solved that problem by 3D-printing Grade 91 steel using a powder bed fusion process with carefully tuned laser settings. The rapid heating and cooling that occurs during printing creates a microstructure unlike anything achievable through traditional steelmaking, and the printed steel is up to 85% stronger at 600°C than its conventionally made counterpart while remaining just as ductile. A granted U.S. patent (US 11,471,946 B2) protects both the manufacturing method and the resulting material. Value Proposition AddiSteel HT gives manufacturers the ability to produce complex steel parts that hold up far better under extreme heat than today's standard materials. Because the process uses commercially available Grade 91 powder and standard industrial 3D printers, adoption does not require exotic raw materials or entirely new equipment. The performance gains are significant enough that printed ferritic steel could serve as a lower-cost alternative to nickel-based superalloys in many high-temperature applications, opening the door to lighter, cheaper and more geometrically creative component designs across the energy and industrial sectors. How it Works A laser selectively melts thin layers of steel powder, one on top of another, to build a solid part from the ground up. LANL's innovation lies in a proprietary combination of laser power, scanning speed and layer orientation that produces an unusually fine and complex grain structure with a combination of ductile and strong grains during printing. The steels thermal history during the build process creates the microstructure distribution of around 80 % by volume Bainitic grains with a uniform distribution of second phase particles and dislocations, surrounded by 20 % by volume Martensitic grains. This is fundamentally different from what conventional casting or forging can achieve. Each new layer also partially heat-treats the layer beneath it, so the finished part may need little or no additional processing before use. Technical Description Conventional Grade 91 steel relies on a tempered martensite structure that loses strength significantly at high temperatures. The additive process instead produces a layered architecture containing multiple distinct microstructural zones within each laser pass, including regions with extremely fine grains, regions rich in strengthening precipitates and small pockets of martensite at the boundaries between passes. Working together, these features resist deformation at elevated temperatures far more effectively than the uniform microstructure of wrought steel. Testing confirms the advantage across the board. At 600°C, the printe…

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