Creep Behavior of Compact γ′-γ″ Coprecipitation Strengthened IN718-Variant Superalloy

Metals

Semanti Mukhopadhyay¹  Yunzhi Wang¹  Michael J. Mills¹  Gopal B. Viswanathan¹  Hariharan Sriram¹  Christopher H. Zenk²  Richard DiDomizio³  Andrew J. Detor³  Robert W. Hayes⁴ 

[1] Department of Materials Science & Engineering, The Ohio State University, Columbus, OH 43210, USA;Department of Materials Science and Engineering, Institute WTM, Friedrich-Alexander-University Erlangen-Nürnberg, Martensstr. 5, D-91058 Erlangen, Germany;General Electric Global Research Center, Niskayuna, NY 12309, USA;Metals Technology Inc., Northridge, CA 91324, USA;

关键词: superalloy;    IN718;    creep;    microstructure;    compact;    coprecipitates;   

DOI  :  10.3390/met11121897

来源: DOAJ

【 摘 要 】

The development of high-temperature heavy-duty turbine disk materials is critical for improving the overall efficiency of combined cycle power plants. An alloy development strategy to this end involves superalloys strengthened by ‘compact’ γ′-γ″ coprecipitates. Compact morphology of coprecipitates consists of a cuboidal γ′ precipitate such that γ″ discs coat its six {001} faces. The present work is an attempt to investigate the microstructure and creep behavior of a fully aged alloy exhibiting compact coprecipitates. We conducted heat treatments, detailed microstructural characterization, and creep testing at 1200 °F (649 °C) on an IN718-variant alloy. Our results indicate that aged IN718-27 samples exhibit a relatively uniform distribution of compact coprecipitates, irrespective of the cooling rate. However, the alloy ruptured at low strains during creep tests at 1200 °F (649 °C). At 100 ksi (689 MPa) load, the alloy fails around 0.1% strain, and 75 ksi (517 MPa) loading causes rupture at 0.3% strain. We also report extensive intergranular failure in all the tested samples, which is attributed to cracking along grain boundary precipitates. The results suggest that while the compact coprecipitates are indeed thermally stable during thermomechanical processing, the microstructure of the alloy needs to be optimized for better creep strength and rupture life.

【 授权许可】

Unknown