Effects of Boron and Zirconium on Grain Boundary Morphology and Creep Resistance in Nickel-Based Superalloy
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Grain boundaries (GBs) in nickel-based superalloys have a significant influence on the creep resistance of these alloys. In this study, the trace elements of boron and zirconium were added to the newly designed LESS 1 (Ni-22Cr-20Co-2W-2Nb-1.5Al-1.5Ti-0.03C) alloy, and their effects on the GB precipitation behaviors of carbides were observed. The combined addition of boron and zirconium generates a continuous film structure containing MC carbides and M23(C, B)6-type boro-carbides, as well as a grain boundary γ′. Based on the change in microstructure, rupture time is significantly increased. According to the observed microstructures and simulation results, it was confirmed that boron forms M23(C, B)6-type boro-carbides and zirconium appears to stabilize MC carbides at GBs.
Keywordsboron boro-carbide precipitates nickel-based superalloy creep resistance grain boundary zirconium
This work was supported by the Technology Innovation Program (10052860, Development of Superalloys and Manufacturing Technologies for the Rotor/Casing of the 700 °C grade HSC Steam Turbine), which is funded by the Ministry of Trade, industry, and Energy (MI, Korea).
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