A New Polycrystalline Co-Ni Superalloy

作者：Knop M^*; Mulvey P; Ismail F; Radecka A; Rahman K M; Lindley T C; Shollock B A; Hardy M C; Moody M P; Martin T L; Bagot P A J; Dye D

来源：JOM, 2014, 66(12): 2495-2501.

DOI：10.1007/s11837-014-1175-9

In 2006, a new-ordered L1(2) phase, Co-3(Al,W), was discovered that can form coherently in a face-centered cubic (fcc) A1 Co matrix. Since then, a community has developed that is attempting to take these alloys forward into practical applications in gas turbines. A new candidate polycrystalline Co-Ni gamma/gamma%26apos; superalloy, V208C, is presented that has the nominal composition 36Co-35Ni-15Cr-10Al-3W-1Ta (at.%). The alloy was produced by conventional powder metallurgy superalloy methods. After forging, a gamma%26apos; fraction of similar to 56% and a secondary gamma%26apos; size of 88 nm were obtained, with a grain size of 2.5 mu m. The solvus temperature was 1000 degrees C. The density was found to be 8.52 g cm(-3), which is similar to existing Ni alloys with this level of gamma%26apos;. The alloy showed the flow stress anomaly and a yield strength of 920 MPa at room temperature and 820 MPa at 800 degrees C, similar to that of Mar-M247. These values are significantly higher than those found for either conventional solution and carbide-strengthened Co alloys or the gamma/gamma%26apos; Co superalloys presented in the literature thus far. The oxidation resistance, with a mass gain of 0.08 mg cm(-2) in 100 h at 800 degrees C, is also comparable with that of existing high-temperature Ni superalloys. These results suggest that Co-based and Co-Ni superalloys may hold some promise for the future in gas turbine applications.

• 出版日期2014-12