Laser powder bed fusion of a novel CoNi-based high entropy superalloy

Abstract

Laser powder bed fusion (L-PBF) is poised to revolutionize the manufacturing of high-value metallic materials, allowing for intricate, geometrically complex designs while minimizing material waste. The primary challenge lies in formulating alloys compatible with L-PBF that also maintain properties suitable for the demanding conditions encountered in energy, space, and nuclear applications. We introduce a category of high strength, defect-resistant octonary CoNi-based high entropy superalloy (CoNi-HESA), comprising roughly equal parts of Co and Ni, along with Cr, Al, V, Ti, Ta, and W. This alloy exhibits as-printed tensile strength exceeding 1 GPa and tensile ductility exceeding 30 % at room temperature. Furthermore, compression tests demonstrate that the as-printed parts maintain a yield strength of about 1 GPa at room temperature up to 700 °C, which decreases to 0.9 GPa and 0.7 GPa as the test temperature reaches 800 °C and 900 °C, respectively. With a careful combination of laser powder and scan speed, the developed HESA is well-suited for crack-resistant, high-density component production through L-PBF. Alloy design principles are elucidated through CALPHAD calculations based on the high entropy alloy (HEA) database, including the structure and properties of L-PBF processed CoNi-HESA.