Abstract
Microstructures, elemental partition behavior, phase stabilities and mechanical properties of Nb- and W-containing Co-V-Ti-based superalloys were investigated. Elemental partition coefficients (KX = Cγ’/Cγ) 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.
Highlights
Superalloys are widely used in fabricating critical parts in gas turbines of power plants, aircraft engines and chemical process industries, where the current operating temperatures have reached1600 ◦ C [1,2,3,4,5]
Nickel-based superalloys strengthened by γ’ (L12 )-precipitates phase are the most commercially successful among all classes [3,6]
The operating temperatures of Nickel-based superalloys have exceeded 80% of their incipient melting temperatures, fractions that are higher than any other class of engineering alloys
Summary
Superalloys are widely used in fabricating critical parts in gas turbines of power plants, aircraft engines and chemical process industries, where the current operating temperatures have reached1600 ◦ C [1,2,3,4,5]. Superalloys are widely used in fabricating critical parts in gas turbines of power plants, aircraft engines and chemical process industries, where the current operating temperatures have reached. Nickel-based superalloys strengthened by γ’ (L12 )-precipitates phase are the most commercially successful among all classes [3,6]. The operating temperatures of Nickel-based superalloys have exceeded 80% of their incipient melting temperatures, fractions that are higher than any other class of engineering alloys. Cobalt-based superalloys are often considered as possible alternatives to Nickel-based superalloys whose solidus and liquidus are 50–150 ◦ C lower than the former [7]. All common alloying elements for superalloys have lower diffusion coefficients and lower stacking fault energies in cobalt than in nickel [8]
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