Effect of Ta additions on microstructure and mechanical properties of a single-crystal Co–Al–W-base alloy

• The addition of Ta is effective to improve the γ′ solvus temperature in Co–Al–W–Ni–Cr alloy system.
• The addition of Ta is beneficial to improve the tensile strength in Co–Al–W–Ni–Cr alloy system.
• The addition of Ta is beneficial to improve the creep strength in Co–Al–W–Ni–Cr alloy system.

Microstructures and mechanical properties of Co–9.5Al–5W–16Ni–6Cr–xTa (at% where x=0, 1.8, 2.8, named as 0Ta, 1.8Ta and 2.8Ta) alloys are investigated. Microstructures of heat-treated samples are composed of γ and cubical γ′ precipitates. The γ′ solvus temperature increases obviously with Ta additions. The yield strength as well as creep strength is improved with the addition of Ta. Ta additions affect the high-temperature tensile deformation mechanism. The γ′ phase of the three alloys is rafted along the tensile axis direction during creep tests at 900 °C. The creep strength of 2.8Ta alloy is approaching the level of a first-generation Ni-base single-crystal superalloy.