Superalloys 2021: Tuesday Interactive Session on Disk Alloy Manufacture & 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 10:10 AM
September 14, 2021
Room: Poster Area
Location: Virtual Event
Phenomenological Modeling of the Effect of Oxidation on the Creep Response of Ni-based Single-crystal Superalloys: Jean-Briac le Graverend1; Seungjun Lee1; 1Texas A&M University
A new constitutive equation predicting the evolution of oxide thickness is proposed and implemented in a crystal plasticity framework with a hardening-based damage density function. The oxidation model depends on the initial surface roughness as well as the amount of accumulated plastic strain and stress triaxiality. The effect of oxidation on the mechanical behavior and damage is considered at the flow stress level by modifying the amplitude of the kinematic hardening. The oxidation-altered kinematic hardening is able to predict the effect of oxidizing environments on the mechanical behavior, specifically the plastic strain rate in the secondary creep stage, and lifetime. In addition, the oxidation model has also been tested in 3D by performing a finite-element simulation on a notched specimen subjected to a creep load. It revealed that the model is able to predict surface roughness and oxide thickness distributions in 3D and for multiaxial stresses.
Microstructural Effects on Creep Properties in a Co-base Single Crystal Superalloy: Haijing Zhou1; Longfei Li2; Stoichko Antonov2; Qiang Feng2; 1Central Iron & Steel Research Institute; 2University of Science and Technology Beijing
In our previous study, Co-Al-W-Ta-Ti quinary alloys were found to show excellent creep resistance at elevated temperature. In order to clarify the influence of the initial microstructure on the creep behavior of a Co-base single crystal superalloy, the tensile creep behavior of the Co-base alloy with different initial microstructures was investigated at 900 °C and 420 MPa and the relationships between the initial microstructures and the creep properties, such as the rupture life and the minimum creep rate, were analyzed. It is suggested that the ă′ size increased with increasing aging time or temperature, while the volume fraction of this Co-base alloy remained similar through heat treatments at 900 and 1000 °C for 50 - 1000 h. Moreover, the initial dislocation density also increased with increasing aging time, but varied negligibly with higher aging temperature. On the other hand, four distinct creep stages were observed during the creep process, and the rupture life exhibited an optimum peak as a function of ă′ size, which was also influenced by the initial ă/ă′ lattice misfit. Meanwhile, the minimum creep rate increased with an increase of the initial dislocation density. This study can serve as a guide for future microstructural design and optimization of Co-Al-W-base superalloys.
Tensile, Low Cycle Fatigue and Very High Cycle Fatigue Characterizations of Advanced Single Crystal Nickel-based Superalloys: Luciana Maria Bortoluci O1; Satoshi Utada1; Jérémy Rame2; Lorena Mataveli Suave3; Kyoko Kawagishi4; Hiroshi Harada4; Patrick Villechaise1; Jonathan Cormier1; 1Ensma/Pprime; 2Safran Aircraft Engines; 3Safran Tech; 4National Institute for Materials Science (NIMS)
Tensile and fatigue life variabilities are investigated for new-generation single crystal Ni-based superalloys: the 3rd generation CMSX-4 Plus, the 6th generation TMS-238, and a newer Ni-based superalloy, TROPEA containing Pt. Consistently from the results of previous research, very high cycle fatigue (VHCF) properties at the chosen condition of T = 1,000 °C/ Rĺ = −1/f = 20 kHz, are mainly influenced by the solidification/homogenization pore size and position. TROPEA alloy has the best low cycle fatigue (LCF) life among all tested alloys at 650 °C and Ró = 0.05/f = 0.5 Hz. To better understand the influence of chemical composition on the LCF endurance, tensile properties were investigated using nine different single crystalline alloys at 650 °C with the strain rate of 5×10-4 s-1. The yield stress is directly affected by the chemical composition of the Ni-based superalloys, and alloys with high contents of Ti and Ta have a higher yield stress, due to an increased shearing resistance of g′ precipitates. Hence, the yield stress is the main control parameter of LCF at the selected condition. No influence of chemical composition on VHCF life durability has been observed, in good agreement with previous studies.
Competing Mechanism of Creep Damage and Stress Relaxation in Creep-fatigue Crack Propagation in Ni-base Superalloys: Shiyu Suzuki1; Motoki Sakaguchi1; Ryota Okamoto1; Hideaki Kaneko2; Takanori Karato2; Kenta Suzuki2; Masakazu Okazaki3; 1Tokyo Institute of Technology; 2Mitsubishi Heavy Industries, ltd.; 3Nagaoka University of Technology
Effect of creep deformation at crack tip on fatigue crack propagation behavior in a single crystal and a directionally solidified superalloys at 900 °C was investigated. Creep-fatigue crack propagation tests with single tension hold introduced into cyclic fatigue loading were conducted. In specimen extracted from the single crystal superalloy, ICMSX-4, when the cyclic fatigue loading was restarted after the tension hold, nascent crack was immediately initiated followed by significant crack retardation. This crack propagation behavior was ascribed to mechanisms based on two different concepts of residual compressive stress and crack closure. From the viewpoint of mechanism based on the residual stress concept, material degradation at crack tip induced by the tension hold was investigated using scanning electron microscope, while stress relaxation and the resultant residual compressive stress at crack tip were quantified by elastic-plastic-creep finite element analysis coupled with digital image correlation technique. Finally, crack propagation behavior in polycrystalline specimen extracted from the directionally solidified superalloy, MGA1400, was investigated focusing on effect of grain boundary. An insight into criteria of a transition from crack retardation to accelerated intergranular cracking was suggested based on a relative grain size to “creep affected zone”.
An Integrated Hip Heat-treatment of a Single-crystal Ni-base Superalloy: Benjamin Ruttert1; Inmaculada Lopez-Galilea1; Werner Theisen1; 1Ruhr-Universität Bochum
The heat-treatment of a 2nd generation single-crystal Ni-base superalloy was implemented in a hot isostatic press providing fast quenching rates. Thus it is possible to homogenize chemical heterogeneities, close porosity, and to set a fine and uniform ă/ă’-microstructure via fast quenching and subsequent aging in one processing step. The microstructural evolution in dependence of parameters such as temperature, pressure, and quenching is investigated on different length scales using diverse characterization methods. A virtually defect-free microstructure is the outcome of this unique integrated supersolvus HIP heat-treatment.
3 Ton Melting with CaO Desulfurization of Ni-base Single Crystal Superalloy TMS-1700, Simulating a Recycling of Used Turbine Blades: Tadaharu Yokokawa1; Hiroshi Harada1; Kyoko Kawagishi1; Makoto Osawa1; Michinari Yumaya1; Toshiharu Kobayashi1; Takuya Sugiyama1; Shinsuke Suzuki1; Masao Sakamoto1; 1National Institute for Materials Science
In order to investigate the applicability of a direct and complete recycling method to commercial-scale ingot production, 3 tons of a Ni-base single crystal (SC) superalloy, TMS-1700(MGA1700) was melted and desulfurized by CaO during the melting. Sulfur content in the molten alloy was reduced from about 23 ppm to about 2 ppm 60 min after adding granular CaO to the molten alloy. Microstructural observations using SEM and EPMA showed no presence of inclusions caused by CaO addition. Creep rupture lives of the recycle-simulated TMS-1700 were equivalent to that of the standard TMS-1700 under the conditions from 800 °C/735 MPa to 1100 °C/137 MPa. The recycle-simulated TMS-1700 exhibits even better oxidation resistance compared with the standard TMS-1700, which has better oxidation resistance than CMSX-4TM. Thus, it became clear that the CaO desulfurization improves the oxidation resistance of Ni-base superalloys. High cycle fatigue (HCF) properties of the standard and the recycle-simulated TMS-1700 were equivalent. From the results described above, it has been suggested that the application of direct and complete recycling method to commercial-scale ingot production is feasible.
Prediction of Rafting Kinetics of Practical Ni-based Single Crystal Superalloys: Yusuke Matsuoka1; Yuhki Tsukada1; Toshiyuki Koyama1; 1Nagoya University
Directional coarsening of γ′ phase (rafting) in Ni-based single-crystal superalloys during tensile creep at 1273 K is simulated by the phase-field (PF) method. A number of PF simulations are performed with various values of PF model parameters. The obtained results are used to train a neural network (NN) to enable fast and accurate prediction of the rafting time (trafttraft) from the values of model parameters. Material parameters of first-, second-, third-, and fourth-generation superalloys are estimated from their chemical compositions for predicting trafttraft using the trained NN. The trafttraft of several practical superalloys are predicted in the tensile stress range of 130–190 MPa. The NN prediction results show that trafttraft tends to be longer along with the order of alloy generation. Furthermore, creep rupture time (truptrup) of practical superalloys is estimated based on the Larson–Miller parameter method. It is found that there is a positive correlation between trafttraft and truptrup, and the correlation becomes stronger with increasing the magnitude of external tensile stress.
Creep Anisotropy in Single Crystal Superalloy DD6 Near the [001] Orientation: Jian Yu1; Jiarong Li1; Shizhong Liu1; Mei Han1; 1Beijing Institute of Aeronautical Materials
This paper has studied the anisotropy in the creep properties of DD6 alloy under different temperatures and applied stresses. The results reveal that the anisotropic creep of DD6 alloy near the [001] orientation is strongly influenced by the temperature in the range of 650 °C to 980 °C. The anisotropy in the primary creep strain and rupture lifetime at an intermediate temperature of 760°C is dependent on the applied stress. Compared with the specimens oriented close to the [001]–[111] boundary, the specimens oriented close to the [001] direction and the [001]–[011] boundary exhibit lower primary creep strains and longer rupture lifetimes at intermediate temperatures and high applied stresses. With the increase in the testing temperature or the decrease in the applied stress, the anisotropic creep behavior of the alloy near the [001] orientation disappears. The mechanism of anisotropic creep is attributed to heterogeneous ă' precipitate deformation by <112>{111} slip.
High-resolution Diffraction Imaging of Misorientation in Ni-based Single Crystal Superalloys: Robert Albrecht1; Maciej Zubko1; 1University of Silesia
In the present work, the novel high-resolution X-ray diffraction technique for imaging misorientation and mosaicity in single crystal superalloys is introduced. The technique is based on classical X-ray diffraction topography geometries combined with high-resolution diffraction and post-processing of obtained data including color coding and 3D projections of each diffraction images. For the investigations, the single crystal rods were produced from CMSX-4 superalloy at a withdrawal rate of 1, 3, 5 and 7 mm·min-1. The high spatial and angular resolution of the method allows to visualize the complex nature of mosaicity present in single crystal superalloys. It was observed that mosaics blocks differ in size and misorientation on the multi-scale level from the small present in dendrite arms, through single dendrites, group of dendrites, up to subgrains. Measurements of misorientation were done on cross and longitudinal sections of the castings. It was proved that increasing withdrawal rate influences the mosaicity structure and mechanisms of its evolution. Solidification at withdrawal rates from 1 to 5 mm·min-1 possesses higher misorientation between dendrites. With higher misorientation between dendrites, when the widening of solidification front occurs, the mosaicity spread across the casting in the form of misoriented dendrite lines as the solidification progress by growing long secondary dendrite arms. Also, it was stated that 3-5 mm·min-1 rates possess a higher possibility of creation of subgrains or selector grains defects in the casting.
Equations to Predict the Elastic Modulus of the Individual Gamma and Gamma-prime Phases in Multi-Component Ni-base Superalloys: Takuma Saito1; Makoto Osawa2; Tadaharu Yokokawa2; Hiroshi Harada2; Toshiharu Kobayashi2; Kyoko Kawagishi2; Shinsuke Suzuki1; 1Waseda Univesity; 2National Institute for Materials Science
Strength of Ni-base single-crystal superalloys under high temperature and low stress creep usually is enhanced by formation of ă/ă′ raft structure and larger aspect ratio of ă′ phase in the ă/ă′ raft structure. Elastic misfit between ă and ă′ phases is one of the most important factors to control the aspect ratio of the ă′ phase in the ă/ă′ raft structure formed under external stress. The aspect ratio of the ă′ phase is controlled by kinetics for the ă/ă′ raft structure formation, which is affected by a strain inhomogeneity caused by this elastic misfit between the ă and ă′ phases under external stress. To realize a new alloy design approach to control the aspect ratio of the ă′ phase in the ă/ă′ raft structure, this research aimed to obtain the regression equations which can predict elastic modulus of the individual ă and ă′ phases for multi-component Ni-base single-crystal superalloys based on measurements of elastic modulus of Ni-base single-crystal alloys. Elastic modulus of the individual ă and ă′ phases of various kinds of Ni-base single-crystal alloys were measured by using Rectangular Parallelepiped Resonance (RPR) method. Using the analyzed and referenced elastic modulus, regression equations for predicting <100> longitudinal elastic modulus of the individual ă and ă′ phases and its temperature and composition dependence were obtained. Detailed analysis of the elastic modulus and its composition dependence was executed to clarify the contribution of each element on the elastic modulus. At 900 °C, Re, Ta, Ti, Al, and Mo reduce the <100> longitudinal elastic modulus in the ă phase. On the other hand, Ru, Re, Ta, Ti, Al, W, and Mo enlarge the elastic modulus in the ă′ phase.
Metallurgical Mechanisms Upon Stress Relaxation Annealing of the AD730™ Superalloy: Malik Durand1; Jonathan Cormier2; Patrick Villechaise2; Jean-Michel Franchet3; Christian Dumont4; Nathalie Bozzolo1; 1Mines ParisTech - CEMEF; 2Institut P'; 3SafranTech; 4A&D Ancizes
Fine microstructural analyzes have been performed to identify the microstructural mechanisms controlling stress relaxation during aging heat treatment of AD730TM disk superalloy. Morphological evolution of the hardening g′ precipitates and plastic activity occur during relaxation tests. For a 500 MPa initial stress, the relaxation test shows atypical behavior with sluggish relaxation in the first hours, and then a faster one. To understand this atypical behavior, isothermal dilatometry tests were used to decouple the effects of stress and temperature. The later revealed a contraction of the specimen when subjected to a constant temperature. This contraction induces a tendency for an increase in stress during the relaxation test to meet the imposed condition of constant total deformation. Relaxation is then controlled by the competition between the classical relaxation mechanisms (vacancies diffusion and/or dislocation gliding) which tend to lower the stress and the contraction of the specimen which tends to increase the stress during the test.
Crystal Plasticity Mechanism of Temperature Dependent Crack Propagation in a Single Crystal Nickel Based Superalloy: Xiaosheng Chen1; Motoki Sakaguchi1; Shiyu Suzuki1; Hirotsugu Inoue1; Masakazu Okazaki2; 1Tokyo Institute of Technology; 2Nagaoka University of Technology
Temperature dependent fatigue crack propagation in a Ni-based single crystal superalloy was experimentally and numerically investigated in a single crystal Ni-base superalloy. Fatigue crack propagation tests at room temperature, 300 °C, 450 °C and 700 °C were conducted using four types of compact specimens with different combinations of crystal orientations in loading and crack propagation directions. It was revealed in the experiments that the crack propagated along slip planes in crystallographic cracking manner at room temperature, while the cracking mode transitioned from the Mode I to crystallographic cracking at 300 °C, 450 °C and 700 °C. Mode I stress intensity factor range ÄKI values at the transitions depended on the testing temperature as well as crystal orientation. To interpret these temperature dependent crack propagation, a crystal plasticity finite element analysis was conducted by taking into account the 3D inclined crack plane and the activity of slip planes in front of the crack. Slip plane activity, proposed as a damage parameter, could rationalize the fatigue crack propagation rates both during the crystallographic and Mode I cracking. It has been found that crack propagation resistance for crystallographic cracking is more or less the same at low temperature, while that for Mode I cracking decreases with the increase of the temperature. This damage parameter also provided an explanation of the critical condition that induces the transition from Mode I to crystallographic cracking.
Metallurgical Analysis of Direct Aging Effect on Tensile and Creep Properties in Inconel 718 Forgings: Alexis Nicola˙1; Jean-Michel Franchet2; Nathalie Bozzolo1; Jonathan Cormier3; 1CEMEF - Mines-ParisTech; 2Safran SA; 3Institut Pprime
Performing the double aging thermal treatment on Inconel 718 forged components directly after forging instead of the standard thermal treatment sequence including a solution annealing step before the double aging is known to be beneficial to mechanical properties. In this work, this so-called direct aging (DA) effect has been assessed for tensile properties at room temperature and for creep properties at 650 °C/750 MPa. Mechanical characteristics obtained on direct aged specimens are compared to those obtained on specimens submitted to the standard thermal treatment sequence (i.e. including a solution heat treatment) and tested in the same conditions. The classical effect of direct aging thermal treatment is obtained, better tensile and creep properties are reached for DA specimens. However, contrary to what is generally assumed, fine microstructural characterizations in specimen heads reveal that the direct aging effect cannot be attributed to a higher residual strain hardening level preserved in the microstructure. It is actually shown that its beneficial effect on mechanical properties is due to a lower d phase content obtained in microstructures having undergone such a treatment rather than the standard sequence. On the one hand, it has indeed been demonstrated that, counter-intuitively, the d phase content actually increased during the “solution” treatment performed at 955 °C for 1h. On the other hand, the relationship between mechanical properties and microstructural features (grain size, d phase content, residual forging strain hardening level) has been analyzed in detail and differences in mechanical behavior are mainly controlled by this increased amount of d phase which deteriorates the mechanical properties. On the contrary, no significant effect of residual forging strain hardening on tensile and creep properties has been found for the investigated conditions.