High Temperature Creep Properties of Advanced Structural Materials: Creep Behavior of Superalloys
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee
Program Organizers: Gianmarco Sahragard-Monfared, University of California, Davis; Mingwei Zhang, Lawrence Berkeley National Lab; Jeffery Gibeling, University of California, Davis
Monday 8:30 AM
March 20, 2023
Room: Sapphire P
Location: Hilton
Session Chair: Gianmarco Sahragard-Monfared, University of California, Davis; Mingwei Zhang, Lawrence Berkeley National Laboratory; Jeffery Gibeling, University of California, Davis
8:30 AM Introductory Comments
8:35 AM Invited
A Microstructure Sensitive Model to Account for the Non-isothermal Creep Behavior of Ni-based Single Crystal Superalloys: Jonathan Cormier1; 1ENSMA - Institut Pprime - UPR CNRS 3346
Nickel-based single crystal superalloys are widely used for the design of aeronautic and industrial gas turbine blades and vanes due to their superior mechanical properties especially in creep up to 1,100°C. A reliable design of these components against creep deformation should take into account all creep stages, creep anisotropy and degradation of the microstructure occurring not only during high temperature creep (rafting) but also during non-isothermal transients. Microstructural parameters are γ' morphology and dislocation structures. The **POLYSTAR** model was developed to fulfill these requirements. New internal variables were introduced in a crystal plasticity framework to take into account microstructure evolutions such as γ' dissolution/precipitation and dislocation recovery processes, and their effects on the creep behavior and creep life. In this presentation, the development of this model will be recalled and examples of engine-like tests (i.e. certification tests) performed on test-bars will be presented to assess the model.
9:05 AM
Creep and Creep-ratcheting Behaviour of Selective Laser Melted (SLM) Additively Manufactured (AM) Inconel 718: Vincent Masse-Denicourt1; Hosea Watson1; Milo Kral1; 1University of Canterbury
The high-temperature performance of Selective Laser Melted (SLM) Additively Manufactured (AM) Inconel 718 is of interest for aerospace applications subject to cyclic thermally-induced stresses. To gain a better understanding of the mechanical performance and material behavior the high-temperature tensile, creep and creep-ratcheting properties at 1000°C have been measured. Creep-ratcheting performance was tested at various stress levels. The microstructural evolution has been investigated at various stages in the creep-ratcheting life to evaluate the accumulated damage. The results of the work will provide insight into the design and service life of components.
9:25 AM
Creep and Tensile Properties of Five Novel, Computationally Designed Ni-based SX Superalloys: Abel Rapetti1; Cervellon Alice1; Menou Edern2; Rame Jérémy3; Cormier Jonathan1; 1Institut Pprime UPR CNRS 3346; 2Safran Tech; 3Safran Aircraft Engines
Computational design is a promising approach used in particular to predict novel compositions for new generation Ni-based single crystal superalloys. Amongst the existing approaches, some allows the exploration of new compositional fields by predicting, for eachcomposition, the ideal performances after optimization of heat treatments. Such approach does not provide, however, directions to optimize heat treatments, which remain to be determined by a classical approach. Five nickel-based single crystalline superalloys were cast with computationally designed compositions. This work was undertaken to determine heat treatments that lead to the target microstructure for the five alloys as well as improved creep strength. Once this target was reached, tensile and creep tests were carried out. In this presentation, we will more specifically detail the high temperature creep properties of theses five alloys and the tensile resistance within a wide range of conditions.
9:45 AM Cancelled
On the High Temperature Strength of Single Crystal Ni-base Superalloys: Marc Sirrenberg1; David Bürger1; Alireza Parsa1; Stefan Guth2; Gunther Eggeler1; 1Ruhr-University Bochum; 2Karlsruher Institut für Technologie (KIT)
For single crystal Ni-base superalloys constant strain rate (CSR) tensile testing, creep testing and anisothermal out of phase thermo mechanical fatigue (TMF) testing are under the most prominent laboratory test methods. In the present work, precisely [001] oriented specimens are used to compare these three types of tests. CSR and creep tests are performed in the temperature range of 750°C to 950°C and TMF tests are performed using these two temperatures as Tmin and Tmax respectively. Emphasis is placed on analyzing how high temperature plasticity manifests itself in the three types of tests, which are all affected by elementary micro creep processes. Moreover, the effect of γ' particle size (at constant γ' volume fraction) receives attention. It is shown that there is a need to compare the three types of testing for one well characterized material and precisely oriented specimens.
10:05 AM Break
10:20 AM Invited
The Elevated Temperature Creep, Fatigue, and Fracture Behavior of Nickel-based Superalloys Manufactured by Direct Metal Laser Sintering: Michael Kassner1; Theophil Oros1; Kwangtae Son2; Lyle Levine3; Thien Phan4; 1University of Southern California; 2Oregon State University; 3National Institute of Standards and Technology; 4Lawrence Livermore National Laboratory
Elevated temperature creep and fatigue experiments were performed on long term cyclically heat treated wrought and additively manufactured (AM) Inconel 718. The creep strength of the AM Inconel was equal or superior to that of the wrought alloy. However, the elevated-temperature ductility of the AM alloy was clearly inferior to that of the wrought alloy. The elevated-temperature fatigue strength of the AM 718 was also inferior to that of the wrought alloy. These results were comparable to our earlier work on Inconel 625. NanoSIMS, APT, SEM and TEM analyses were conducted on the Inconel 718. The basis for the increase in strength and loss in ductility will be discussed.
10:50 AM
Creep Behavior at Elevated Temperatures of Several Polycristalline Ni-based Superalloys Strengthened by MC-carbides: Patrice Berthod1; Safa Tlili1; Dame Assane Kane1; 1University of Lorraine
Conventional casting allows producing components with complex geometries and coarse grains favorable for good creep resistance at high temperatures. Their weak points are generally their intergrains and interdendrites boundaries. Introducing carbon and MC-former metals can achieve the development of an intergranular and interdendritic network of eutectic carbides bringing the double benefit of a script-like geometry for the interdendrites cohesion, and of a good morphological and volume fraction stability on long times at high temperature.In this work two kinds of superalloys were obtained by high frequency induction foundry under inert atmosphere. The first ones are nickel-based superalloys and reinforced by ZrC carbides. The second ones are also nickel-based alloys but strengthened by (Ta,Hf)C carbides. All were subjected to 3-points bending creep tests at 1100°C for a maximal induced tensile stress equal to 20 MPa. They demonstrated high resistance despite the test temperature particularly high for superalloys produced by classical foundry.
11:10 AM
Effect of the Casting Process on the Microstructure and Creep Properties of a Cast Ni-Based Alloy: Govindarajan Muralidharan1; Jiten Shah2; Ram Krishnamurthy3; James Myers4; 1Oak Ridge National Laboratory; 2PDA LLC; 3Haynes International; 4MetalTek International
Generation 3 Concentrated Solar Power Systems are being targeted for operating temperatures greater than 700°C. Ni-based alloy such as Haynes®282® has the potential to satisfy the high temperature mechanical property requirements but cost and availability are major factors to be considered in its use. Components such as piping, pump and valve bodies can be manufactured at a lower cost using casting processes and hence can be produced on demand. This talk will present the effect of casting processes and part geometry on the microstructure, high temperature tensile and short-term creep properties of Haynes®282® and compare these with that obtained from traditional wrought processing. This work was supported by the US Department of Energy - Solar Energy Technologies Office Concentrating Solar Thermal Power Program. This research was conducted by Oak Ridge National Laboratory, which is managed by UT Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE).
11:30 AM
Threshold Creep Behaviour of Ni-based Superalloy IN740H: Chandan Kumar1; Pavan A.H.V.2; Praveen Kumar3; 1Interdisciplinary Centre for Energy Research, Indian Institute of Science, Bangalore; 2BHEL Corporate R&D Division, Hyderabad; 3Indian Institute of Science, Bangalore
Creep deformation of nickel-based superalloy IN740H was studied at temperatures of 750 and 800 °C. The samples were aged at 800 °C after solution-treatment from 4 to ~10,000 h. The tests were performed in compression at a stress in the range of 200 to 450 MPa. The apparent stress exponent, n, changed from 4.5 at 800 °C to 10 at 750 °C. However, effect of prior aging was not observed on the stress exponent. The apparent activation energy, Qc, was calculated to be 565 kJ/mol. The high values of apparent n at 750 °C and Qc suggest a threshold behaviour, i.e., a critical stress value below which creep would not occur. By applying the concept of threshold stress, the true stress exponent and activation energy were calculated to be 4 and 298 kJ/mol, respectively. Subsequently, structure-property correlation was established using transmission electron microscopy and atom probe tomography.
11:50 AM
Induction of Alternative Shearing Pathways during Creep Deformation of Nickel Based Superalloys via Local Phase Transformation Strengthening: Ashton Egan1; Fei Xue2; Emmanuelle Marquis2; Michael Mills1; 1Ohio State University; 2University of Michigan
Deformation of nickel-based superalloys during intermediate temperature creep is dominated by planar defects and microtwinning, where shearing processes are controlled by diffusion mediated segregation and reordering. Local Phase Transformation (LPT) strengthens alloys via formation of η/χ at the defects. Novel LPT strengthening has recently been shown along microtwin boundaries through correlative controlled Electron Channeling Contrast Imaging (cECCI) and Scanning Transmission Electron Microscopy (STEM) studies. This LPT obstructs additional shearing partial dislocations from thickening microtwins, thus preventing rapid strain accumulation. In response, strain alternatively accumulates via deformation induced formation of ordered-HCP “nano-laths”; these are associated and grow from LPT at microtwin interfaces and appear formed by otherwise twin-inducing partials. Advanced characterization of deformation processes was conducted utilizing cECCI, probe corrected STEM, and atomic resolution Energy Dispersive X-Ray Spectroscopy (EDS) to confirm lattice site occupancies.