Influence of rhenium on the hardness, structure and phase composition of the cobalt‑niobium and cobalt‑tantalum alloys

• Published in: International journal of refractory metals & hard materials 2024-06, Vol.121, p.106630, Article 106630
• Main Authors: Fedorayev, Ivan I., Kerimov, Elshat Yu, Leonov, Alexander V., Philippova, Svetlana E., Maksimov, Sergey V., Kalmykov, Konstantin B., Slyusarenko, Evgen M.
• Format: Article
• Language: English
• Subjects: Age hardening; Crystal structure; Heat-resistant alloys; Solid-solution hardening; Tempering; Vickers hardness
• ISSN: 0263-4368; 2213-3917
• DOI: 10.1016/j.ijrmhm.2024.106630

The processes of dispersion hardening of the cobalt‑niobium and cobalt‑tantalum alloys belonging to the fcc-solid solution based on cobalt jointly alloyed with rhenium are studied using scanning electron microscopy, local X-ray spectrum analysis, X-ray phase analysis, transmission electron microscopy, differential scanning calorimetry, and Vickers hardness measurements. Alloying with rhenium significantly increases the hardness of the cobalt‑niobium and cobalt‑tantalum alloys with the fcc-structure, since rhenium stabilizes the Co3Nb and Co3Ta phases and prevents the growth of their particles, thereby contributing to the preservation of the reticulated nanoscale structure. It is shown, that decomposition of the γCo-solid solution at 1200 K is accompanied by formation and growth of the Guinier-Preston zones, occurrence of the Suzuki atmospheres and subsequent formation of the metastable nanoscale Co3Nb and Co3Ta particles with the Mg3Cd-type of the crystal structure. [Display omitted] •Alloying with rhenium increases the hardness of the fcc-Co-(Nb/Ta) alloys.•Alloying with rhenium promotes the formation of the metastable Co3(Nb/Ta) phases.•The metastable Co3(Nb/Ta) phases form between the γNb/Ta- and εCo-phases.•The metastable Co3(Nb/Ta) phases belong to the Mg3Cd-type of the crystal structure.•Alloying with rhenium slows down the growth of the Co3(Nb/Ta) and Laves phases.