Superalloys 2021: Tuesday Part III - Blade and Disk Alloy Behavior
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

Tuesday 1:30 PM
September 14, 2021
Room: Live Session Room
Location: Virtual Event

Session Chair: Stephane Forsik, Carpenter Technology Corporation; Ian Dempster, Wyman Gordon /PPC

1:30 PM
An Approach Towards Understanding Unstable Gamma Prime Precipitate Evolution and Its Effect on Properties: Nicholas Krutz¹; Chen Shen²; Mallikarjun Karadge²; Ashton Egan¹; Justin Bennett³; Timothy Hanlon²; Michael Mills¹; ¹Ohio State University; ²GE Research; ³GE Aviation
    The evolution of gamma prime precipitates generated from supersolvus solution heat treatment and controlled continuous cooling of two powder metallurgy (PM) disk superalloys are characterized and modeled. Variation in cooling rate for these alloys shows a tendency for unstable precipitate growth with slower rates. The degree to which this variation is observed in terms of its effect on particle spacing and deformation-induced defect interaction has not been well characterized previously. To better understand this effect, a series of lab heat treatments of varied cooling rates have been carried out and the mechanical response quantified via elevated temperature tensile tests followed by characterization. A phase-field based approach is used to simulate the growth instability of gamma prime precipitates during slow continuous cooling, the simulated particle morphologies are compared to post-mortem characterization of lab-scale coupons using Focused Ion Beam (FIB) serial sectioning and volumetric reconstruction. Phase-field modeling is then used to interrogate the interaction of the particle morphology with planar dislocation evolution. It was determined that the incipient stages of particle evolution are dictated by interface growth instability more so than elastic anisotropy effects. Planar deformation in the presence of these larger, more evolved particles tended to promote Orowan looping, while smaller particles with smaller gamma channel widths showed a tendency for stacking fault formation under the conditions characterized. These observations suggest that particle morphology is a secondary effect to the overall alloy strengthening mechanism.

1:55 PM
High-temperature Pre-deformation and Rejuvenation Treatment on the Microstructure and Creep Properties of Ni-based Single Crystal Superalloys: Satoshi Utada¹; Jérémy Rame²; Sarah Hamadi²; Joël Delautre²; Lorena Mataveli Suave³; Patrick Villechaise⁴; Jonathan Cormier⁴; ¹Institut Pprime/Safran Aircraft Engines; ²Safran Aircraft Engines; ³SAFRAN Tech; ⁴Institut Pprime
    Unintentional plastic deformation during production of turbine blades made from Ni-based single crystal superalloy has a huge risk on its durability. In the present study, a plastic deformation was applied at various temperatures to AM1 alloy and its effect on the alloy’s microstructure and creep properties were analyzed. Microstructure evolution during aging treatment was different for plastic deformation at lower temperature (≤ 750 °C) and higher temperature (950 °C) because of different deformation mechanisms. AM1 with mild ă′ directional coarsening after plastic deformation at 950 °C and following aging treatments performed well in creep test at 1050 °C/140 MPa, but poorly at 850 °C/500 MPa. Rhenium containing CMSX-4 Plus was tested similarly to AM1. Pre-deformation has huge impact on creep durability of CMSX-4 Plus at 1150 °C/110 MPa, however, the creep life debit at 1050 °C/200 MPa was minor. In order to restore properties of pre-deformed single crystal superalloys, rejuvenation heat-treatment process was added after pre-deformation. Rejuvenation treatment successfully restored microstructure after room-temperature plastic deformation, and creep properties of rejuvenated specimens are equivalent to that of original AM1 and CMSX-4 Plus.

2:20 PM
Tuning Strain Localization in Polycrystalline Nickel-based Superalloys by Thermomechanical Processing: Marie Charpagne¹; Jean-Charles Stinville¹; Andrew Polonsky¹; McLean Echlin¹; Sean Murray¹; Zhe Chen¹; Nathalie Bozzolo²; Jonathan Cormier³; Valery Valle³; Tresa Pollock¹; ¹University of California, Santa Barbara; ²CEMEF Mines ParisTech; ³Institut Pprime
    Thermomechanical processing routes are used to produce microstructures that minimize plastic strain localization at the sub-grain scale in a polycrystalline γ−γγ−γ’ nickel-based superalloy. This novel approach is made possible by the use of innovative experimental tools and statistical data analysis that capture slip events over large representative fields of view. Results are correlated to conventional observations of fatigue crack initiation and early stage of propagation. The effect of coherent twin boundaries and primary γ′γ′ precipitates on fatigue properties and plastic localization is detailed.

2:45 PM Question and Answer Period