Superalloy 718 and Derivatives: High Temperature Fe-, Ni- , and Co- Alloys
Program Organizers: Joel Andersson, University West; Chantal Sudbrack, National Energy Technology Laboratory; Eric Ott, GE Additive; Zhongnan Bi, Central Iron and Steel Research Institute
Tuesday 1:00 PM
May 16, 2023
Room: Admiral
Location: Sheraton Pittsburgh Hotel at Station Square
Session Chair: Timothy Smith, NASA Glenn Research Center; Kevin Bockenstedt, ATI Specialty Materials
1:00 PM Introductory Comments
1:05 PM Invited
Factors Influencing Propensity for Stress Relaxation Cracking in Inconel ® Alloy 740H® and Practical Guidance for Applications: John Shingledecker1; John Siefert1; Tapasvi Lolla1; John Dupont2; John DeBarbadillo3; Ronnie Gollihue3; 1Electric Power Research Institute; 2Lehigh University; 3Special Metals Corporation
Inconel® Alloy 740H® (UNS N07740) was the first age-hardenable nickel-based alloy approved by the ASME Boiler & Pressure Vessel Code for use in pressure-boundary applications. In recent years, advanced energy systems such as supercritical CO2 power cycles have utilized alloy 740H in large demonstration projects driven by the requirement for higher fluid temperatures and pressures. Stress relaxation cracking (SRxC) following post-weld heat-treatment (PWHT), also known as strain age cracking (SAC), has been identified in a limited number of weldments during these industrial builds resulting in focused research to further clarify factors influencing this cracking tendency. This paper will summarize some of the findings from shop and field fabrication leading to successful welds and characteristics of observed SRxC. Laboratory experiments supported by microstructural characterization will be presented to highlight the importance of variables such as strain, material starting condition, and PWHT temperatures. Finally, the results will be summarized within the context of practical guidance for industry to successfully weld the material in boiler, heat exchanger, and piping applications.
1:35 PM
Mechanical and Microstructural Properties of Brazed Honeycomb Liner Material Haynes 214: Jonas Vogler1; Jieun Song2; Jakob Huber3; Rainer Völkl4; Uwe Glatzel4; 1University of Bayreuth; 2Karlsruhe Institue of Technology; 3Technical University of Munich; 4University Bayreuth
Honeycomb sealing systems are used in aircraft turbines to minimize leakage air in the gaps between rotating parts and the turbine casing in order to improve efficiency and thus reducing carbon dioxide emission [1]. The honeycomb structure of sealings protects the fins of the rotating turbine blades from critical damage when a contact caused by thermal or mechanical expansion occurs [2]. The honeycombs itself are point welded thin metal sheets of a nickel-based superalloy brazed on to a substrate usually also made of a nickel-based superalloy. During the brazing process braze filler alloy is drawn into gaps between the metal sheets by capillary forces. In this work the mechanical performance of Haynes 214 metal sheets brazed with the nickel-chromium-silicon braze filler BNi 5 (71 wt.% Ni, 19 wt.% Cr, 10 wt.% Si) is investigated. Tensile properties of as brazed metal sheet composites are tested. Interdiffusion zones and hard particles with high chromium contents are observed along the brazed joint. Even a very thin brazing layer reduces the ductility considerably. References [1] H. L. Stocker, D.M. Cox and G.F. Holle NASA Report, 1977, No. NASA-CR-135307.[2] D. Sporer and D. Fortuna Welding Journal, 2014, Volume 93(2),44–48.
1:55 PM
(LBN - P4) Laser-Powder Bed Fusion Additive Manufacturing of Haynes 282 Concentrating Solar-Thermal Power (CSP) Plant Parts: Printability, Geometry, Surface, and Microstructure.: Junwon Seo1; Nicholas Lamprinakos1; Anthony Rollett1; 1Carnegie Mellon University
Laser powder bed fusion (L-PBF) additive manufacturing has been successful in fabricating simple geometries using high-temperature materials such as Inconel 718 and Haynes 282 (H282). However, printing larger and more complex geometries can be challenging due to the variations in thermal profiles adjacent to the melt pool compared to printing simple geometries. We describe the fabrication of part-scale specimens, including molten salt-to-supercritical CO2 heat exchangers and supercritical CO2 solar receivers, for concentrating solar-thermal power (CSP) generation. The specimen designs were optimized to maximize performance while ensuring printability and resistance to high temperatures and pressures by printing and analyzing sub-scale units. The effects of various process parameters, including scan strategy, laser power, and scanning speed, on the density, surface roughness, and microstructure at various regions of the complex geometries were investigated. Furthermore, the effects of heat treatment on large-scale specimens were investigated to ensure mechanical integrity throughout the components.
2:15 PM Cancelled
Effect of Heat Treatment on the Mechanical Property and Deformation Mechanism of a Novel Cast Nickel-base Superalloy: Pengfei Zhao1; Min Wang1; Xianchao Hao1; Weiwei Xing1; Meiqiong Ou1; Yingche Ma1; Kui Liu1; 1Institute of Metal Research, Chinese Academy of Sciences
A novel cast nickel-base superalloy named K4800 is developed, which can be used at 800-850℃. The yield and ultimate tensile strengths of K4800 can reach 780 and 910Mpa at 800℃ with an elongation no lower than 7%, and the creep life of K4800 is generally not less than 120h under 870℃/255MPa. Meanwhile, this material has outstanding microstructural stability at 800 and 850℃ without the precipitation of σ and η phase during long-term aging. The microstructure of K4800 consists of γ, MC, M23C6, and the γ' in two sizes, following the heat treatment of solution annealing plus double-stage aging. Accurate control of the content and proportion of the γ' phases in two dimensions is the key to obtaining an optimal mechanical property of K4800. With the decrease of large-sized and the increase of small-sized γ' in content, the material is gradually strengthened by paired dislocations shearing without an apparent ductility drop.
2:35 PM Break