A Study on the Formation of Serrated Grain Boundaries and its Applications in Nimonic 263

Abstract:

The formation of serrated grain boundaries and its subsequent effect on creep resistance have been investigated in a wrought nickel based superalloy Nimonic 263. The grain boundaries were considerably serrated without the presence of γ' phases or M23C6 when a specimen was slow-cooled from the solution treatment temperature. The high resolution observation on the lattice image of the serrated grain boundary suggested that the grain boundaries tended to serrate to have specific segments approaching to one {111} low-index plane at a boundary in order to have lower interfacial free energy of grain boundary. The grain boundary serration led to a change in M23C6 carbide characteristics: the carbide morphology from granular to planar, a lowered density and their coherency pattern to two neighboring grains from consistent to zigzag. The improvement of creep resistance was noticeably observed by the introduction of GB serration without deterioration of basic mechanical properties. This improvement in creep resistance by the serration was associated with a lower rate of cavitation and crack propagation through the modification of carbide characteristics as well as grain boundary configuration.

• Periodical: Materials Science Forum (Volumes 638-642)
• Pages: 2245-2250
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.638-642.2245
• Online since: January 2010
• Authors: Hyun Uk Hong, Hi Won Jeong, In Soo Kim, Baig Gyu Choi, Young Soo Yoo, Chang Yong Jo
• Keywords: Carbide, Creep, Grain Boundary Serration, Heat Treatment, Nimonic 263

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