ECI Digital Archives

Title

Microstructure, tensile behavior and oxidation resistance of the two step heat treated Nb- Ti-Si based alloy

Authors

Hu Zhang, Beihang University, ChinaFollow
Chungen Zhou, Beihang University, China
Jiangbo Sha, Beihang University, China
Lei Zheng, Beihang University, China
Lina Jia, Beihang University, China

Conference Dates

July 17-21, 2016

Abstract

Although the temperatures of the hottest section of advanced turbine engines are approaching the limit of nickel-based superalloys, the desire for continued performance improvements for gas turbine engines continues [1]. Nb-Ti-Si based alloys have attracted much attention for their high temperature melting points, relatively low densities and excellent high temperature mechanical properties [2]. In this alloy system, the constitute phases are niobium solid solution (Nb_SS), silicides (Nb₅Si₃ and / or Nb₃Si) and with / without Cr₂Nb. Among these phases, Nb_SS ensures room temperature fracture toughness and tensile strength, silicides offers high temperature strength, and Cr₂Nb provides the oxidation resistance [3].In this study, the Nb-Ti-Si based alloy was firstly prepared by arc-melting and then directional solidification at a rapid speed. Two-step heat treatments were carried out on the directionally solidified Nb-Ti-Si based alloy. The first-step heat treatment was performed at 1375, 1400, 1425 and 1450 °C for 10hours, respectively. According to the microstructure characteristic and their resulting tensile strength, the best condition for the first-step heat treatment is 1425 °C/10 h. Then the second step heat treatment was conducted at 1000, 1100, 1200 and 1300 °C for 50 hours, respectively. The precipitation of nano-scale Cr₂Nb particles in the Nb_SS matrix substantially improved the tensile strength from 850 MPa to 950 MPa, and reduced the weight gain of the alloy from 218.27 to 144.41mg/cm² by the second step heat treatment at 1000 °C.

References

[1] B. P. Bewlay, M. R. Jackson, P. R. Subramanian, J. C. Zhao, Metall. Mater. Trans., 34A (2003) 2043-2052

[2] L.N. Jia, J.F. Weng, Z. Li, Z. Hong, L.F. Su, H. Zhang. Mater. Sci. Eng., 623A (2015) 32-37

[3] L. F. Su, L. N. Jia, Y. B. Feng, H. R. Zhang, S. N. Yuan, H. Zhang, Mater. Sci. Eng., 560A(2013) 672-677

Recommended Citation

Hu Zhang, Chungen Zhou, Jiangbo Sha, Lei Zheng, and Lina Jia, "Microstructure, tensile behavior and oxidation resistance of the two step heat treated Nb- Ti-Si based alloy" in "Beyond Nickel-Based Superalloys II", Chair: Dr Howard J. Stone, University of Cambridge, United Kingdom Co-Chairs: Prof Bernard P. Bewlay, General Electric Global Research, USA Prof Lesley A. Cornish, University of the Witwatersrand, South Africa Eds, ECI Symposium Series, (2016). https://dc.engconfintl.org/superalloys_ii/66