Superalloys 2021: Pre-Conference Live Talks
Program Organizers: Sammy Tin, University of Arizona; Christopher O'Brien, ATI Specialty Materials; Justin Clews, Pratt & Whitney; Jonathan Cormier, ENSMA - Institut Pprime - UPR CNRS 3346; Qiang Feng, University of Science and Technology Beijing; Mark Hardy, Rolls-Royce Plc; John Marcin, Collins Aerospace; Akane Suzuki, GE Aerospace Research

Wednesday 8:30 AM
September 8, 2021
Room: Live Session Room
Location: Virtual Event

Session Chair: Akane Suzuki, GE Aerospace Research; Vikas Saraf, ATI Ladish

8:30 AM
Evaluation and Comparison of Damage Accumulation Mechanisms during Non-isothermal Creep of Cast Ni-based Superalloys: Stoichko Antonov¹; Wenrui An¹; Satoshi Utada²; Xiaotong Guo¹; Caspar Schwalbe³; Weiwei Zheng¹; Cathie Rae³; Jonathan Cormier²; Qiang Feng²; ¹University of Science and Technology Beijing; ²ISAE-ENSMA; ³University of Cambridge
    The creep behavior under non-isothermal and isothermal creep conditions was studied for a single crystal, a directionally solidified, and a polycrystalline superalloy. Regardless of the alloy type, the non-isothermal creep life of the alloy was much lower than that under isothermal conditions, yet the samples ruptured at higher plastic strains. Irregular interfacial network formation and early (but homogeneously distributed) shearing of the ă' phase was identified as the main source of damage for all three alloys. Additionally, secondary precipitates with thermal expansion coefficients different from the surrounding matrix, led to the formation of creep voids, especially under thermal cycling. In that respect, surface carbides were seen as particularly damaging due to their selective oxidation, which resulted in the extension of secondary cracks. The higher plastic strains exhibited by the non-isothermal creep samples were correlated to the more homogeneously distributed damage accumulation, in comparison to the more localized deformation during isothermal creep. This study provides an overview of the damage accumulation sources in the three types of available superalloys, and highlights areas which need to be further considered when designing future alloys for the non-isothermal creep regime.

8:55 AM
Precipitate Phase Stability and Mechanical Properties of Alloy 263 and Variants in Wrought or Cast Form: Martin Detrois¹; Paul Jablonski¹; Jeffrey Hawk¹; ¹National Energy Technology Laboratory
    Alloy 263 is a candidate Ni-based superalloy for use in advanced ultra-supercritical (AUSC) power plants that are targeted to operate above 700 °C. Exposure times in this type of environment are considerable with target creep properties specified at 100,000 h making phase stability an important parameter in the alloy selection process. In this investigation, the microstructure of alloy 263 and two modified compositions in both cast and cast/wrought forms were investigated after exposure at 800 °C for various times ranging from 1,000 h to 10,000 h. Tension and creep properties were assessed for all alloys in both forms. Modification to the Ti and Al concentrations successfully slowed down the ă′ to ç transformation while doubling the ă′ fraction. Thin elongated ç needles or platelets formed in the wrought products while thicker, plate-like, ç precipitates were found in the castings. The effect of the various microstructures on the creep properties were determined using isothermally aged specimens aged at 800 °C for 3,000 h and 10,000 h prior to creep screening. Strong precipitation of the ç phase was found to considerably decrease creep life and increase minimum creep rate. By modifying the Ti and Al content, the creep life and ductility of the new formulation tested on specimens isothermally aged for 3,000 and 10,000 h were near that of the nominal alloy in its standard aged condition.

9:20 AM
Effect of Carbide Inoculants Additions in IN718 Fabricated by Selective Laser Melting Process: Tzu-Hou Hsu¹; Kai-Chun Chang¹; Yao-Jen Chang¹; I-Ting Ho²; Sammy Tin³; Chen-Wei Li⁴; Koji Kakehi⁴; Chih-Peng Chen⁵; Kuo-Kuang Jen⁵; Ho-Yen Hsieh⁶; An-Chou Yeh¹; ¹National Tsing Hua University; ²Illinois Institute of Technology; ³University of Arizona; ⁴Tokyo Metropolitan University; ⁵National Chung-Shan Institute of Science and Technology; ⁶Gloria Material Technology Corp.
    This article presents the effect of carbide inoculants additions on microstructure evolution and mechanical properties of Inconel 718 superalloy fabricated by selective laser melting (SLM) process. Flakes of titanium carbide (TiC) and niobium carbide (NbC) were mixed with the Inconel 718 powder and acted as nucleating agents to induce heterogenous nucleation in order to eliminate anisotropic grain structure. By increasing fraction of carbide inoculants, more isotropic grain texture was detected. Furthermore, significant improvements on creep properties have been observed with minor carbide additions. With 0.5 wt % TiC and NbC addition, creep rupture life could be increased from 198.5 hours to 449.5 hours and 371.8 hours, respectively. Moreover, creep strain rate was dramatically decreased from 0.513 10-8 s-1 to 0.12 10-8 s-1 by 0.5 wt % TiC additions. This study has demonstrated that minor carbide addition can have profound impact on the microstructure and property of Inconel718 processed by SLM.

9:45 AM Question and Answer Period