Effects of Nb and W Additions on the Microstructures and Mechanical Properties of Novel γ/γ’ Co-V-Ti-Based Superalloys

摘要

Microstructures, elemental partition behavior, phase stabilities and mechanical properties of Nb- and W-containing Co-V-Ti-based superalloys were investigated. Elemental partition coefficients ( K X = C γ’ /C γ ) of Nb and W in Co-V-Ti-based superalloys are 2.07 and 1.10, respectively. The γ’ solvus temperatures are determined as 1023 °C, 1055 °C and 1035 °C in Co-12V-4Ti, Co-10V-4Ti-2Nb and Co-10V-4Ti-2W alloys, which are higher than those of Co-9Al-9W alloy (1000 °C). The mass densities of quaternary Co-10V-4Ti-2Nb and Co-10V-4Ti-2W alloys are about 8.31 and 8.50 g·cm ?3 , respectively, which are 15% lower than Co-Al-W-based superalloys (9.8 g·cm ?3 ). All examined alloys exhibit an anomalous positive dependence on temperature rising from 600 to 750 °C. Strengths of all examined alloys are higher than those of MarM509 (traditional Cobalt-based superalloy) and Co-9Al-9W at all temperatures that we investigated. The maximum flow stress of Co-V-Ti-Nb alloy is about 638 MPa at 750 °C while that of Co-V-Ti-W alloy is about 588 MPa at 700 °C.