Accelerated discovery of oxidation resistant CoNi-base γ/γ’ alloys with high L12 solvus and low density

A defect-resistant Co–Ni superalloy for 3D printing

“…These results are shown in Table 1. Apparent distribution coefficients measured in Bridgman-grown SXs of SB-CoNi-10 show the same partitioning tendencies as the EBM sample 40 . The degree of partitioning in SB-CoNi-10 is much lower in comparison to conventional Ni-base alloys, resulting in the variation of the fraction liquid with temperature also being lower 40 .…”

“…Apparent distribution coefficients measured in Bridgman-grown SXs of SB-CoNi-10 show the same partitioning tendencies as the EBM sample 40 . The degree of partitioning in SB-CoNi-10 is much lower in comparison to conventional Ni-base alloys, resulting in the variation of the fraction liquid with temperature also being lower 40 . Since the length-scale of the segregation present in the as-printed cellular structure is smaller than the interaction volume of the EPMA electron probe, it is not possible to resolve the apparent distribution coefficients for the SLM sample.…”

“…Calculations indicated that Ti, Ta, Nb, and Ni were favorable alloying additions. Creep experiments on several SX variants of these materials confirmed that alloys with these elements possessed creep strengths that exceeded first generation SX Ni-base superalloy levels 39,40 .…”

“…Starting from the composition of an alumina-forming IPD alloy of composition Co-32.4Ni-11.7Al-4.4W-3.3Cr-1.5Ta (at.%), three additional alloys with small variations in composition were arc melted into 40 g buttons 40 . After analysis of microstructure and phases present, a final composition, SB-CoNi-10, possessing a desirable two-phase microstructure was selected for (a) SX growth to measure basic properties and (b) 3D printing to assess its behavior in both laser and electron beam based PBF methods.…”

“…The SB-CoNi-10 alloy has a nominal composition of Co–36.4Ni–13.2Al–6Cr–3.5Ta–1W (at.%) along with minor additions of 0.08B–0.08C–0.018Hf–0.002Y which are included for grain boundary strengthening, carbide formation, and oxide scale adhesion 40 . It possesses a high volume fraction of of ~0.7 after aging at 1000 °C, a mass density similar to Ni-base superalloys (8.65 g cm −3 ), and is able to form environmentally protective α -Al 2 O 3 after high-temperature exposure in air 40 , 54 .…”