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Korean Journal of Metals and Materials > Volume 56(1); 2018 > Article
Korean Journal of Metals and Materials 2018;56(1): 8-13. doi: https://doi.org/10.3365/KJMM.2018.56.1.8
니켈기 초내열합금의 감마프라임상의 성장거동
오준협1, 조대영1, 김홍규2, 윤존도1,3
1경남대학교 대학원
2국방과학연구소
3경남대학교 나노신소재공학과
Growth Rate of Gamma Prime Precipitates in Ni-Base Superalloy
Junhyeob Oh1, Daeyoung Jo1, Hongkyu Kim2, Jondo Yun1,3
1Department of Advanced Engineering, Graduate School, Kyungnam University, Changwon 51767, Republic of Korea
2Agency for Defense Development, Daejeon 34186, Republic of Korea
3Department of Nano Materials Engineering, Kyungnam University, Changwon 51767, Republic of Korea
Correspondence  Jondo Yun ,Tel: +82-55-249-2697, Email: jdyun@kyungnam.ac.kr
Received: 4 August 2017;  Accepted: 29 September 2017.  Published online: 1 January 2018.
ABSTRACT
The mechanical properties of nickel-base superalloys used in disk and blade materials for gas turbine engines can be maximized by controlling their microstructure, such as the size of precipitates. In this study, we investigated the size of gamma prime precipitates after age hardening heat treatment at 650-980 oC for 1-48 hours. As the aging temperature and time increased, the grain size of gamma prime increased. The growth constants were 0.11, 0.24, 15.5 and 167 nm3/sec at 650, 760, 870, and 980 oC respectively. Activation energy for the growth of the gamma prime precipitates was determined to be 261±54 kJ/mol and reference studies have confirmed that Ni, Al, or Ti lattice diffusion in Ni or Ni3Al dominates the rate. The hardness increased with the decreasing size of gamma prime precipitates, and reached maximum at 24 nm, and decreased thereafter. The data on hardness vs. precipitate size followed the Hall-Petch relation over a precipitate size range from 24 nm to hundreds of nanometers. The maximum hardness at each annealing time increased with a reduction in the annealing temperature time. The optimum condition was determined to be 727 oC and 24 hours by using an approximation curve. The maximum hardness (520HV) was experimentally confirmed under this condition. The reduction in hardness with decreasing size might be due to changes in the misfit strain at the interface, decrease in the gamma prime volume fraction, or an increase in particle cutting events by dislocation.
Keywords: Ni-base superalloy, aging, activation energy, hardness
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