Comparison of the stress relaxation and creep behavior of conventionally forged and additively manufactured René 65

• Published in: Journal of materials science Vol. 58; no. 13; pp. 5951 - 5969
• Main Authors: Tiparti, Dhruv, Wessman, Andrew, Cormier, Jonathan, Tin, Sammy
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.04.2023; Springer; Springer Nature B.V; Springer Verlag
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Comparative analysis; Condensed Matter; Creep strength; Crystallography and Scattering Methods; deformation; Forgings; Heat treating; Heat treatment; High temperature; Materials Science; Metals & Corrosion; Microstructure; Nickel base alloys; Physics; Polymer Sciences; Powder beds; Solid Mechanics; Stress relaxation; Superalloys; temperature; Turbine disks; Turbines; microstructure; deformation mechanism; size; perspective; model; mobile dislocation density; nickel-based superalloys
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-023-08399-2

René 65 is a high strength cast & wrought (CW) Ni-base superalloy with thermomechanical performance tailored toward intermediate temperature and stress conditions (677 °C/690 MPa). René 65 Turbine disk rotor forgings are typically subject to a sub-solvus heat treatment utilized to retain a uniform and fine-grained microstructure that confers a high level of fatigue performance and strength at the expense of high-temperature creep resistance. However, the processing of René 65 via laser powder bed fusion (LPBF) can enable this material to exhibit intermediate or coarse-grained microstructures after heat treatment that possess improved creep resistance. The effect of the difference in the processing route in conjunction with heat treatment on the resulting microstructure is presented and correlated to the creep behavior (at 677 °C/690 MPa) and stress relaxation behavior (700 °C). A good correlation of relaxation and creep behaviors was found, with LPBF processed René 65 exhibiting overall improved resistance to high-temperature deformation. The primary factor with regards to microstructural difference toward the stress relaxation/creep behavior of René 65 has been identified to be the size and volume fraction of tertiary γ ’ present resulting from the chosen processing pathway.