Achieving superior elevated temperature properties in additive manufactured nickel-based superalloys through unique alloy design

Abstract

Additive manufacturing (AM) offers a new solution for the integrated fabrication of complex components, supplementing the shortcomings of conventional subtractive manufacturing. However, the forming defects owing to alloy unsuitability and the lack of long-term service stability of the components seriously limit its widespread engineering applications. Here we developed a nickel-based superalloy, Haynes 230AM, suitable for AM by using Zirconium (Zr) alloying strategy in Haynes 230 alloy, which is crack-free and has outstanding elevated temperature properties. Compared with commercial Haynes 230 alloy fabricated by rolling and AM, the printed Haynes 230AM in our work achieves about 700 % improvement in creep lifetime, breaking the status quo that the creep properties of AM fabricated alloys are generally inferior to the corresponding conventional manufactured alloys. Our results reveal that the introduction of Zr element optimized the microstructure of the alloy. The superior creep resistance of Haynes 230AM stems from the uniform distribution of fine ZrC carbide, the precipitation of Ni7Zr2 phase along close-packed planes and the formation of unique matrix distortion stripes, which impede dislocation motion and delay the formation of creep defects. Moreover, the Zr element can also improve internal oxide scales, reduce oxidation weight gain by 20 % and does not deteriorate the mechanical properties after long-term thermal exposure. These results can provide guidance for the design of high-performance AM-specific superalloys.