High-strength Damascus steel by additive manufacturing

• Published in: Nature (London) Vol. 582; no. 7813; pp. 515 - 519
• Main Authors: Kürnsteiner, Philipp, Wilms, Markus Benjamin, Weisheit, Andreas, Gault, Baptiste, Jägle, Eric Aimé, Raabe, Dierk
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 25-06-2020; Nature Publishing Group
• Subjects: 3D printing; 639/166/988; 639/301/1023/1026; Additive manufacturing; Alloys; Aluminum; CAD; Computer aided design; Computer-aided manufacturing; Cooling rate; Damascus process; Design; Elongation; Fabrication; Hand forging; Heat treating; Heat treatment; Heat treatments; Hierarchies; High strength steels; Humanities and Social Sciences; Lasers; Manufacturing industry; Martensite; Martensitic transformations; Mechanical properties; Metal powders; Methods; Microstructure; multidisciplinary; Nickel; Precipitates; Precipitation; Precipitation hardening; Precipitation hardening steels; Precipitation heat treatment; Process parameters; Production processes; Science; Science (multidisciplinary); Steel; Steel, High strength; Tensile strength; Thermal cycling; Three dimensional models; Titanium; Germany
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-020-2409-3

Laser additive manufacturing is attractive for the production of complex, three-dimensional parts from metallic powder using a computer-aided design model
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. The approach enables the digital control of the processing parameters and thus the resulting alloy’s microstructure, for example, by using high cooling rates and cyclic re-heating
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. We recently showed that this cyclic re-heating, the so-called intrinsic heat treatment, can trigger nickel-aluminium precipitation in an iron–nickel–aluminium alloy in situ during laser additive manufacturing
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. Here we report a Fe19Ni5Ti (weight per cent) steel tailor-designed for laser additive manufacturing. This steel is hardened in situ by nickel-titanium nanoprecipitation, and martensite is also formed in situ, starting at a readily accessible temperature of 200 degrees Celsius. Local control of both the nanoprecipitation and the martensitic transformation during the fabrication leads to complex microstructure hierarchies across multiple length scales, from approximately 100-micrometre-thick layers down to nanoscale precipitates. Inspired by ancient Damascus steels
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—which have hard and soft layers, originally introduced via the folding and forging techniques of skilled blacksmiths—we produced a material consisting of alternating soft and hard layers. Our material has a tensile strength of 1,300 megapascals and 10 per cent elongation, showing superior mechanical properties to those of ancient Damascus steel
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. The principles of in situ precipitation strengthening and local microstructure control used here can be applied to a wide range of precipitation-hardened alloys and different additive manufacturing processes.
A Damascus-like steel consisting of alternating hard and soft layers is created by using a laser additive manufacturing technique and digital control of the processing parameters.