Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 28    No. 3    March 2018

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Effect of cooling rate on microstructure and tensile properties of powder metallurgy Ni-based superalloy
Han-hui DING1,2, Guo-ai HE1,2, Xin WANG1,2, Feng LIU1,2, Lan HUANG1,2, Liang JIANG1,2

1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; 2. Powder Metallurgy Research Institute, Central South University, Changsha 410083, China

Abstract:The effects of size distribution, morphology and volume fraction of γ′ phase and grain size on tensile properties of powder processed Ni-based superalloy were investigated by using two different quenching methods. Oil quenching and air cooling were adopted with cooling rate of 183 °C/s and 4-15 °C/s, respectively. The experimental results show that the average size of the secondary γ′ after oil quenching is 24.5 nm compared with 49.8 nm under air cooling, and corresponding volume fractions of γ′ are 29% and 34%, respectively. Meanwhile, the average grain size remains nearly equivalent from both oil-quenching and air-cooling specimens. The tensile strength at room temperature is higher for the oil-quenched specimen than the equivalent from the air-cooled specimen, but the difference approaches each other as the temperature increases to 650 °C. The fractography clearly demonstrates that transgranular fracture governs the failure process at ambient temperature, in contrast to the intergranular fracture at 650 °C or even higher temperature. These two mechanical responses indicate the strengthening effects of γ′ precipitates and grain boundary for polycrystalline Ni-based superalloys at different temperatures.

 

Key words: powder metallurgy Ni-based superalloy; cooling rate; tensile properties; γ′ phase precipitate; fracture mechanism

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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