Superalloys 2021: Wednesday Interactive Session on Alternative Materials and Additive
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
Wednesday 3:10 PM
September 15, 2021
Room: Poster Area
Location: Virtual Event
Anisotropic Deformation and Fracture Mechanisms of an Additively Manufactured Ni-based Superalloy: Cheng-Han Yu1; Ru Lin Peng1; Mattias Calmunger1; Vladimir Luzin2; Håkan Brodin3; Johan Moverare1; 1Linköping University; 2ANSTO/ NSTLI Neutron Scattering; 3Siemens Industrial Turbomachinery AB
This study investigates the anisotropic mechanical and microstructural behavior of the laser powder bed fusion (LPBF) manufactured Ni-based superalloy Hastelloy X (HX) by using slow strain-rate (10-5s-1 and 10-6s-1) tensile testing (SSRT) at 700˚C. LPBF HX typically exhibits an elongated grain structure along the building direction (BD) and the texture analysis from the combination of neutron diffraction and EBSD discloses a major texture component <011> and a minor texture component <001> along BD, and a texture component <001> in the other two sample directions perpendicular to BD. Two types of tests have been performed, the horizontal tests where the loading direction (LD) is applied perpendicular to BD, and the vertical tests where LD is applied parallel to BD. The vertical tests exhibit lower strength but better ductility, which is explained by the texture effect and the elongated grain structure. A comparison of the mechanical behavior to the wrought HX shows that LPBF HX has better yield strength due to the high dislocation density as proved by TEM images. Creep voids are observed at grain boundaries in SSRT for both directions and are responsible for the poor ductility of the horizontal tests. The vertical ductility in SSRT maintains the same level as the reference tensile test at the strain rate of 10-3s-1, due to the extra deformation capacity contributed by the discovered deformation twinning and lattice rotation. The deformation twinning, which is only observed in the vertical tests and has not been found in the conventionally manufactured HX, is beneficial to maintain the ductility but does not strengthen the material.
Microstructural Control and Optimisation of Haynes 282 Manufactured through Laser Powder Bed Fusion: Katerina Christofidou1; Hon Tong Pang1; Wei Li2; Yogiraj Pardhi2; Colin Jones2; Nick Jones1; Howard Stone1; 1University of Cambridge; 2Rolls-Royce plc
The microstructure and properties of alloy Haynes 282 produced through laser powder bed fusion were investigated as a function of the post-deposition heat-treatment. Scanning electron microscopy and X-ray diffraction were utilised to characterize the microstructure, whilst electro-thermal mechanical testing was used to evaluate the tensile and creep properties at 900˚C. In the as-deposited state, the initial microstructure consisted of the ã and ãʹ phases along with M6C and M23C6 carbides. These carbides were observed to govern the recrystallization behavior of the material and resulted in a minimum recrystallization temperature of 1240˚C. Following post-deposition heat-treatments the microstructures consisted of a monomodal distribution of ãʹ with M6C and M23C6 carbides along the grain boundaries. Tertiary ãʹ particles were found to form in the vicinity of carbides in samples that employed a ãʹ super-solvus step prior to ageing at 788˚C. The tensile properties were found to be similar in all heat-treated states, consistent with the minimal differences observed in the microstructures. In contrast, significant differences in the creep behavior of the alloy was observed following the different heat-treatments, although no correlation with the microstructures was observed.
Additive Manufacturability of Nickel-based Superalloys: Composition-process Induced Vapourisation: Chinnapat Panwisawas1; Yuanbo Tang1; Joseph Ghoussoub1; Roger Reed1; 1University of Oxford
Mass loss due to vaporization induced by the high energy heat source during powder bed fusion additive manufacturing (AM) is one of central issues which concerns the compositional variations across the AM build. Potentially, defects can be initiated where local chemistry in the AM build is not homogeneous. In this work, the evaporation effect of powder bed fusion AM has been first developed in a binary alloy Nitinol (NiTi) and then applied to nickel-based superalloys via physics-based integrated modelling framework and experimental investigation. Volatile species which depart from the nominal composition result in significant mass lost up to 2 atomic percent of Ni in the binary alloy system Nitinol, consistent with energy-dispersive X-ray analysis. As for the multicomponent alloy system of nickel-based superalloys, inductively coupled plasma optical emission spectroscopy (ICP-OES) results reveal further that Al, Co, and Cr are preferable to vaporise first with the loss up to 1.2 atomic percent; this affects the thermal fluid behaviour given that the thermophysical property is altered by composition variations. Hierarchical microstructures have been characterised to rationalise the process-structure-property relationship. The mathematical tool validated with targeted experimentation can be further developed for AM materials design, particularly for taking care of vapourisation.
Castability and Recrystallization Behavior of γ'-strengthened Co-base Superalloys: Nicklas Volz1; Christopher Zenk1; Timur Halvaci1; Katarzyna Matuszewska1; Steffen Neumeier1; Mathias Göken1; 1FAU Erlangen-Nuremberg
Casting of single-crystalline superalloys is known to be difficult due to a variety of challenges. Co-base superalloys, however, promise to show quite good castability compared to Ni-base superalloys, as documented in this manuscript. Therefore, an alloy series, which is designed by changing only the Co- to Ni-ratio is used to address this topic. In addition to the casting behavior, segregation and recrystallization behavior were also investigated, since these are closely related to casting challenges. It was found that in the as-cast state all alloying elements distribute more homogeneously in the Co-rich alloys which is beneficial for casting. Casting of directionally solidified tubes revealed that the Co-rich alloys show a lower susceptibility to hot tearing and predominantly develop cold cracks. Since cold cracking can be addressed by component design, Co-base superalloys are suggested to show a better castability compared to Ni-base superalloys. Recrystallization, however, is more pronounced for the Co-rich alloys. This might become a problem during casting of single crystalline Co-base components, if high deformation is introduced in the solidified component.
Strain Monitoring during Laser Metal Deposition of Inconel 718 by Neutron Diffraction: Sandra Cabeza Sanchez1; Ozcan Burak1; Jonathan Cormier2; Thilo Pirling1; Stefan Polenz3; Franz Marquardt3; Thomas Hansen1; Elena Lopez3; Arantxa Vilalta-Clemente2; Christoph Leyens3; 1ILL; 2Institut Pprime, UPR CNRS 3346, ISAE-ENSMA; 3Fraunhofer IWS
In this study, we provide novel in-situ monitoring of strain during laser metal deposition of Inconel 718 by neutron diffraction. Thermal, phase and stress-related contributions to the lattice parameter evolution are addressed for the representative regions during processing: melt pool, near melt pool and far-field. The evolution showed a strong dependency on the build height and distance to the melt pool, i.e time and temperature gradient, as expected. The different regions of interest reached at different moments the processing stable regime, which is contrasted with microstructural characterization. A homogeneous microstructure of coarse epitaxial dendrites and Laves phase was found from the third printed layer on, with fine globular delta phase precipitation at the grain boundaries. In comparison, neutron diffraction strain monitoring highlighted an offset of process stabilization after 29 layers for the melt pool region, after 12 for near-melt pool region, and after 13 layers for the far-field region.
Development of a New Alumina-forming Crack-resistant High-γ′ Fraction Ni-base Superalloy for Additive Manufacturing: Ning Zhou1; Austin Dicus1; Stéphane Forsik1; Tao Wang1; Gian Colombo1; Mario Epler1; 1Cartech
A new high-ã′ volume fraction Ni-base superalloy for additive manufacturing was developed using a CALPHAD-based approach. Selective laser melting followed by hot isostatic pressing produces a microstructure that is free of microcracks and fusion defects. Post-processing includes a solution-and-age heat treatment to precipitate about 55 vol.% of ã′. Two chemistries with different levels of grain boundary strengthening elements were tested to evaluate the balance between printability and high-temperature properties. After heat treatment, the alloy exhibits 980 MPa yield strength and 1400 MPa ultimate tensile strength at room temperature and maintains that level of yield strength up to 800 °C. Cyclic oxidation tests show good resistance to environmental damage due to the formation of a protective alumina layer.
The Effect of Heat Treatment on Tensile Yielding Response of THE New Superalloy ABD-900AM for Additive Manufacturing: Yuanbo Tang1; Joseph Ghoussoub1; Chinnapat Panwisawas1; David Collins2; Sajjad Amirkhanlou3; John Clark3; Andre Nemeth3; David McCartney1; Roger Reed1; 1University of Oxford; 2University of Birmingham; 3OxMet Technologies
The heat treatment response of the new superalloy ABD-900AM, designed specifically for additive manufacturing (AM), is studied. The as-fabricated microstructure is characterised at multiple length-scales including by X-ray synchrotron diffractometry. The very high cooling rates arising during the process suppress g’ precipitation; thus the details of heat treatment are shown to be important in establishing properties. The yield stress and tensile strength developed are marginally improved by super-solvus rather than sub-solvus heat treatment, but the ductility is then compromised. The tensile behaviour is superior to the heritage alloy IN939 which has a comparable fraction of g’; this is due to the larger refractory content of ABD-900AM and its finer scale precipitation. The internal strains developed during processing are sufficient to promote recrystallization during super-solvus heat treatment which breaks down microstructural anisotropy and promotes grain growth; however, this effect is absent for the sub-solvus case.
Effects of Ti and Cr Additions in a Co-Ni-Al-Mo-Nb Based Superalloy: Nithin Baler1; Prafull Pandey1; Mahander Singh1; Surendra Kumar Makineni1; Kamanio Chattopadhyay1; 1Indian Institute of Science, Bangalore
In the present work, we show the feasibility of microstructural control by additions of Ti and Cr to a /′ Co-30Ni-10Al-5Mo-2Nb superalloy. Solutioning at 1300 ℃ followed by aging at 900 ℃ leads to homogenous distribution of L12 ordered cuboidal ′ precipitates in face-centered-cubic (fcc) matrix. Compositional measurements show Al, Mo and Nb partition to ′ that indicates the ′ can be described as (Co,Ni)3(Al,Mo,Nb). An addition of 2 at.% Ti leads to increases in the ′ volume fraction from 56 % to 70 % and solvus temperature from 990 ℃ to 1030 ℃. Ti strongly partitions to ′ with respect to ã matrix. Similarly, an addition of 10 at.% Cr to the base alloy leads to a morphological transition of ′ precipitates from cuboidal to near spherical shape, indicating a direct influence on the /′ lattice misfit. Unlike Ti, Cr partitions to matrix and additionally, Cr influences Mo to partition into matrix. A combined addition of Ti and Cr leads to high ′ volume fraction ~ 76 % and an increase in solvus temperature to 1045C, while maintaining the spherical ′ morphology. These superalloys show 0.2 % proof strength comparable to those of Co-Al-W based superalloys. At 870 C, 10 at.% Cr and 2 at.% Ti added alloys show higher specific 0.2 % proof stress than Co-Al-W based superalloys. The obtained results show the microstructural sensitivity of these Co-based superalloys towards their designing for better performance.
Machine Learning-assisted Design Approach for Developing γ′-Strengthened Co-Ni-base Superalloys: Min Zou1; Wendao Li1; Longfei Li1; Ji-Cheng Zhao2; Qiang Feng1; 1University of Science and Technology Beijing; 2University of Maryland
As a new class of promising high-temperature materials, Co-Al-W-base alloys have been developed by alloying additions to improve the microstructure stability and other properties. However, the optimization of Co-Al-W-base alloys becomes more complicated with increasing variety and content of alloying elements. In this study, an accelerated approach to design ′-strengthened Co-Ni-base superalloys with well-balanced properties was developed, by integrating the diffusion-multiple approach and machine-learning tools. A large amount of experimental data was obtained using the diffusion-multiple approach and fed into machine learning tools to establish the relationship between alloy compositions and important thermodynamic and microstructural parameters such as the phase constituent, the ã′ phase fraction (Fã′) and the ã′ solvus temperature (Tã′). The established machine-learning models were then employed to predict the characteristic parameters of multicomponent Co-Ni-base superalloys containing up to nine elements (Co, Ni, Al, W, Ta, Ti, Cr, Mo, Nb), even though most of the collected compositions from experiments were quinary to septenary alloys. Using the predicted results from the models and the computational thermodynamics tools, a multicomponent Co-Ni-base superalloy aimed at the application as single crystal blades was designed and characterized to test the reliability and robustness of the novel design approach.
Computational Design of Additively Printable Nickel Superalloys: Adarsh Shukla1; Sanket Sarkar1; Durga Ananthanarayanan2; Raghav Adharapurapu1; Laura Dial3; Sanjay Sondhi1; 1GE Research, Bangalore, India; 2KTH Royal Institute of Technology; 3GE Research, Niskayuna, USA
The recent advances in additive manufacturing (AM) have led to printing of complex structural components. The highly non-equilibrium processing conditions encountered during Direct Metal Laser Melting (DMLM) frequently lead to micro-cracking in high-temperature capable Ni-superalloys, irrespective of processing conditions, limiting their current applicability. This paper aims to develop a general criterion to assess printability of a Ni-superalloy solely based on its composition. Thirty-four Ni-superalloys spanning a wide range of alloying elements were printed, each with twenty-four process conditions, and their crack densities were measured in order to have a consistent set of experimental data for building a model. The models available in literature for predicting cracking susceptibility were evaluated against the experimental data. Finally, a hybrid model, based on physics based quantities, was built with the most significant input features (x’s). This model correlates well with the experimental data and is applicable across a wide range of Ni-superalloy compositions.
Mechanical Performance of a Non-weldable Ni-base Superalloy: Inconel 738 Fabricated by Electron Beam Melting: Michael Kirka1; Peeyush Nandwana1; Sean Yoder1; Patxi Fernandez-Zelai1; Obed Acevedo1; Daniel Ryan2; Mark Lipschutz2; 1Oak Ridge National Laboratory; 2Solar Turbines Incorporated
Additive manufacturing processes are becoming increasingly utilized throughout industry. These technologies enable novel design and manufacture of complex components, reduce material waste streams, and potentially reduce development cycles via rapid prototyping. The high-γ′γ′ Ni-base superalloys are of particular interest to the gas turbine engine industry due their high-temperature resistance. However, as a result of the high γ′γ′ volume fraction, these alloys are traditionally termed non-weldable due to a propensity to crack during welding from a host of mechanisms including hot-tearing and strain-age cracking. These mechanisms are subsequently found in fusion-based additive manufacturing processes. Furthermore, there is a long history of employing traditionally processed components in gas turbine engines, and hence, the performance of materials produced by additive manufacturing needs to be closely investigated. In this work is presented the tensile, high-temperature fatigue, and creep deformation behavior for Inconel 738 fabricated through electron beam melting (EBM) additive manufacturing. Under tensile and fatigue conditions, the material was observed to perform in an isotropic manner when tested parallel and transverse to the build direction. Although under creep conditions, the material exhibited an anisotropy between material tested parallel and transverse to the build direction. With the difference attributed to the fine columnar grain structure observed in the additively manufactured Inconel 738. Ultimately, the EBM material was observed to perform comparably to the conventional cast Inconel 738.