Aging of a New Niobium-Modified MAR-M247 Nickel-Based Superalloy

Author(s)

Baldan, Renato ^[1] ; Soares Azevedo e Silva, Paulo Ricardo ^[1] ; Nunes, Carlos Angelo ^[1] ; Coelho, Gilberto Carvalho ^{[1, 2]}

Affiliation

^[1] Univ Sao Paulo, EEL, Dept Engn Mat DEMAR, BR-12600970 Sao Paulo - Brazil

^[2] UniFoa Ctr Univ Volta Redonda, Nucleo Pesquisa, BR-27240560 Rio De Janeiro - Brazil

• Document type: Journal article
• Source: Journal of Materials Engineering and Performance; v. 22, n. 8, p. 2337-2342, AUG 2013.
• Web of Science Citations: 2

Abstract

MAR-M247 is a nickel-based superalloy that contains 3 wt.% Ta (weight percent of tantalum). Considering the chemical similarity between tantalum and niobium (Nb) and the lower cost of Nb, a modified MAR-M247 superalloy was produced with total replacement of Ta by Nb in this work. The samples were previously solutioned at 1260A degrees C for 8 h and then aged at different times (between 5 and 80 h) and temperatures (between 780 and 980A degrees C). The microstructures of the aged samples were characterized with a scanning electron microscope (SEM and FEG-SEM, both with EDS). Simulations of the MC carbide and gamma' fraction and the Ta and Nb content in both MC carbide and gamma' phase were performed with Thermo-Calc software (TT\_Ni8 database) and simulations of the gamma' growth rate and gamma' mean diameter were performed with JMatPro software. MC carbide with high Hf content was observed in all the aged samples, in agreement with thermodynamic simulation results. The equilibrium gamma' fraction decreases from 67 mol.% at 780A degrees C to 52 mol.% at 980A degrees C. Good agreement between the calculated and experimentally determined gamma' particle size was also found. The growth rate of gamma' at 980A degrees C is about 8 times higher than that at 780A degrees C and 3 times higher than that at 880A degrees C. The hardness values do not change considerably after aging at 780 and 880A degrees C. However, these values decrease significantly after aging at 980A degrees C. (AU)

• FAPESP's process: 10/05211-1 - Directional solidification of Nb modified MAR-M247: processing, microstructural and mechanical characterization
• Grantee: Carlos Angelo Nunes
• Support Opportunities: Regular Research Grants
• FAPESP's process: 09/17337-2 - Heat-treatment and microstructural characterization of Nb-modified MAR-M247 superalloy
• Grantee: Paulo Ricardo Soares Azevedo e Silva
• Support Opportunities: Scholarships in Brazil - Scientific Initiation