Advancing Current and State-of-the-Art Application of Ni- and Co-based Superalloys: Welding, Joining, Rejuvenation, Surface Treatment
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Chantal Sudbrack, National Energy Technology Laboratory; Mario Bochiechio, Pratt & Whitney; Kevin Bockenstedt, ATI Specialty Materials; Katerina Christofidou, University of Sheffield; James Coakley, Chromalloy; Martin Detrois, National Energy Technology Laboratory; Laura Dial, Ge Research; Bij-Na Kim; Victoria Miller, University of Florida; Kinga Unocic, Oak Ridge National Laboratory

Thursday 8:30 AM
February 27, 2020
Room: 11B
Location: San Diego Convention Ctr

Session Chair: Martin Detrois, National Energy Technology Laboratory; Chantal Sudbrack, Northwestern University Center for Atom-Probe Tomography


8:30 AM  Invited
Welding and Weldability Assessment of Ni-based Superalloys: Joel Andersson1; 1University West
     Fabrication and welding of structural components for the hot section of gas turbines continues to be of high importance to the manufacturing industry within this discipline. Weld cracking and specifically hot cracking as well as strain age cracking, is a serious concern during fabrication of these structural components. The aforementioned cracking phenomena can occur during welding or subsequent heat treatment of precipitation hardened Ni- based superalloys and can be influenced by i.e. chemical composition in terms of hardening elements and impurities, microstructure of base material and weld zone, together with welding processes and corresponding parameters and heat input. This paper discusses and reviews the literature with regard to cracking susceptibility of wrought, cast as well as superalloy parts produced by additive manufacturing.

9:00 AM  Invited
Recent Advances in Inertia Friction Welding of Dissimilar Ni-base Superalloys: Oleg Senkov1; David Mahaffey1; S. Lee Semiatin1; 1Air Force Research Laboratory
    Significant differences in the elevated temperature deformation behavior of cast and powder metallurgy superalloys challenge the ability to produce sound bonds of these alloys by inertia friction welding (IFW). The limited plastic flow of the stronger material during welding limits the bond plane ‘‘self-cleaning’’ and mechanical mixing of the mating surfaces, such that defects generally remain at the bond plane after welding. In this talk, recent advances in inertia friction welding of dissimilar Ni-base superalloys are presented. The relationships between the IFW process parameters, welding machine efficiency and welding response are investigated. The kinetics and efficiency of the transformation of the flywheel mechanical energy into frictional heating at the bond plane, kinetics of flash formation, and bond quality are identified. The effect of pre-heating on plastic flow and resulting weld quality is also discussed. Conditions resulting in sound welding are outlined.

9:30 AM  
Structural and Chemical Features of Borides Precipitated within the Transient Liquid (TLP) Bonded Superalloys: Xiaobing Hu1; Vinayak Dravid1; 1Northwestern University
    Boron is widely used as an important melting point depressant (MPD) element in filler materials in transient liquid phase (TLP) bonding, where various kinds of borides will precipitate in the diffusion affect zone (DAZ) and influence the integral mechanical properties of bonded materials. In this talk, we will show the structural and chemical features of M3B2 and M5B3 borides formed in DAZ in a TLP-bonded Ni-based superalloy at atomic scale. Different from previous knowledge that various metallic atoms distributed randomly within M3B2 and M5B3 lattice, by means of atoms resolved element mapping technique, we directly show the chemical ordering within M3B2- and M5B3-type boride. Additionally, the crystallographic orientation relationships (ORs) among M3B2, M5B3 and matrix and their associated interfacial features are defined. The interfacial features between M3B2/M5B3 and matrix, and the unique dendrite intergrowth between M3B2 and M5B3 are also rationalized by means of phase transformation crystallography.

9:50 AM  
On the Rejuvenation of Crept Ni-base Single Crystal Superalloys (SX) by Hot Isostatic Pressing (HIP): Oliver Horst1; Benjamin Ruttert1; David Bürger1; Larissa Heep1; Hongcai Wang1; Antonín Dlouhý2; Werner Theisen1; Gunther Eggeler1; 1Ruhr-Universitaet Bochum; 2Academy of Sciences of the Czech Republic
    In the present study, the effect of HIP-rejuvenation treatments on the creep behavior and residual life of a pre-crept single crystal Ni-base superalloy of type CMSX-4 is investigated. Miniature creep experiments of precisely oriented [001] tensile creep specimens with HIP treatments and quantitative analysis of scanning and transmission electron micrographs are combined. A HIP-rejuvenation treatment after 5.0% creep pre-strain significantly improves creep strength. However, the microstructural damage induced by the creep pre-deformation could not be fully removed. In a series of sequential creep/HIP/creep-experiments, increasing levels of pre-deformation result in increasing levels of creep rates even after identical HIP-rejuvenation treatments. The memory effect, which causes this phenomenon, is related to an accumulation of permanent microstructural damage, which is not associated with rafting or cavitation. The mechanical results obtained in the present work are interpreted based on microstructural results, the pore population and dislocation substructures, which have formed during creep.

10:10 AM Break

10:30 AM  
Heat Treatment Behavior and Microstructure Evolution of Ni-Cr-Mo-W (Haynes 244) Alloy after Surface Treatment by Ultrasonic Nanocrystalline Surface Modification (UNSM) and Laser Shock Peening (LSP): Jie Song1; Anurag Sharma1; Boateng Twum Donkor1; Vijay Vasudevan1; 1University of Cincinnati
    Ni base superalloys are widely used in high temperature environments because of their excellent mechanical properties at elevated temperature, resistance to creep deformation and corrosion. The surface treatments by Ultrasonic Nanocrystalline Surface Modification (UNSM) and Laser Shock Peening (LSP) can play an important role in promoting Ni2(Cr,Mo) precipitation and improving the high temperature behaviors of the Haynes 244 alloy. In this study, Haynes 244 alloy surface treatment were introduced using both UNSM and LSP methods by controlled process parameters, and the microstructure (precipitation identification, gran size, texture, etc.) characterized using electron microscopes. The residual stress, hardness, and mechanical properties distributions from surface to center were also characterized. The results show that UNSM and LSP leads to hierarchically precipitation behavior and exceptional mechanical properties, which will be presented and discussed.

10:50 AM  
Effect of Ultrasonic Nanocrystalline Surface Modification (UNSM) on the Oxidation Behavior of Alloy 800HT in a Supercritical Carbon Dioxide (SCO2) Environment: Richard Chiang1; Sebastien Teysseyre2; Jeffery Aguiar3; Lucas Teeter4; Julie Tucker4; Vijay Vasudevan1; 1University of Cincinnati; 2Canadian Nuclear Laboratories; 3Idaho National Laboratory; 4Oregon State University
    UNSM was utilized in this initial study as a means to alter the surface reactivity of Alloy 800HT and induce surface/sub-surface structures that can readily supply Cr to the interface and reduce the effect of sensitization/carburization in a high temperature SCO2 environment (550°C; 20MPa; 500hrs). An observable increase in surface reactivity, dislocation density and reduction in surface/sub-surface grain size is apparent with notable influence on the development of the multi-layered oxide. Though more optimization of the UNSM treatment is required, reduction in sensitization and carbon at the oxide/matrix interface shows promise as a suitable method of mitigation against degradation.

11:10 AM  
Elevated Temperature Tribological Behavior of Alloys 800HT and 617 for High Temperature Gas-cooled Reactor Applications: Valentin Pauly1; Carter Tesch1; Joseph Kern1; Malcolm Clark1; David Grierson1; Oyelayo Ajayi2; Dileep Singh2; Kumar Sridharan1; 1University of Wisconsin-Madison; 2Argonne National Laboratory
    Incoloy 800HT and Inconel 617 have been selected as candidate structural alloys for the high-temperature gas-cooled reactor (HTGR). The impurities contained in the helium coolant (e.g., H2O, CO2, CH4) can induce corrosion reactions at high temperatures, which can affect the tribological behavior of components in sliding contact. In this study, the high-temperature tribological behavior of the two alloys tested using a pin-on-disk tribometer was observed to vary considerably depending on the type of corrosion product layers on the alloys’ surfaces. The formation of a nanostructured glaze oxide layer due to the high-pressure compaction and sintering of the surface oxide reduced friction and wear. Alloy 617 showed superior wear resistance compared to that of alloy 800HT due to the formation of a Cr- and (Ni, Cr)-spinel oxide layer, rather than Fe-containing oxides. The potential for the mitigation of wear by surface treatments such as aluminization and shot peening was also explored.

11:30 AM  
Friction Stir Welding of Inconel 825 Alloy: Hrishikesh Das1; Mounarik Mondal1; Jiwoo Lee2; Hoon-Hwe Cho2; Sung-Tae Hong1; 1University of Ulsan; 2Hanbat National University
    Friction stir butt welding of inconel 825 alloy has been successfully performed without any microscopic defects. FS welded region consists of mixed pattern with two different regimes: bright region and black banded region. Microstructure and precipitation behavior of both regions have been characterized by SEM, EBSD and TEM assisted EDS analysis. EBSD analysis confirms that stir zone exhibited dynamic recrystallized structure and grain boundary mapping corroborated that no significant changes in the fraction of low and high angle boundaries between SZ, TMAZ and base metal. The frequency of CSL greatly diminished from BM to SZ and TMAZ. TEM analysis shows that nano twins and nano size precipitations dispersed in the grains as well as at the grain boundaries. Grain refinement and nano size precipitations formation at FSW region, enhanced mechanical properties such as micro hardness and tensile strength (all the samples are failed from the BM) to significant amount.