Additive Manufacturing of Metals: Microstructure, Properties and Alloy Development: Ni-based Super Alloys
Program Organizers: Prashanth Konda Gokuldoss, Tallinn University of Technology; Jurgen Eckert, Erich Schmid Institute of Materials Science; Zhi Wang, South China University of Technology
Monday 8:00 AM
October 10, 2022
Room: 302
Location: David L. Lawrence Convention Center
Session Chair: Markus Chmielus, University of Pittsburgh; Jovid Rakhmonov, Northwestern university
8:00 AM
Characterizing the Effects of Laser Power, Scanning Velocity, and Deposition Temperature on Inconel 718 Single-track Melt Pool Geometry in Laser Powder Bed Fusion: William Frieden Templeton1; Seth Strayer2; Shawn Hinnebusch2; Albert To2; Sneha Prabha Narra1; 1Carnegie Mellon University; 2University of Pittsburgh
The quality of laser powder bed fusion (L-PBF) additively manufactured (AM) parts is inherently tied to melt pool characteristics during production. Suboptimal melt pool characteristics lead to porosity and decreased strength in AM parts compared to legacy manufacturing methods. Suboptimal melt pool characteristics are avoided using currently available process windows that guide laser power and velocity selection to avoid the development of defects such as keyhole porosity or lack-of-fusion. In addition to the power and velocity, this study characterizes the impact of deposition temperature on the geometry of single-track Inconel 718 melt pools. This experimental characterization work results in process windows to avoid undesirable melt pool characteristics resulting from heat build-up during fabrication of complex geometries.
8:20 AM
In-situ and Ex-situ Characterization of Inconel 738 Subjected to Additive Manufacturing: Adriana Eres-Castellanos1; Jeremy Shin1; Ruben Ochoa1; Chandler Becker1; Beau Nannie1; Jonah Klemm-Toole1; Alec Saville1; Brian Rodgers1; Kamel Fezzaa2; Amy Clarke1; 1Colorado School of Mines; 2Argonne National Laboratory
Ni-based superalloys are commonly used in aerospace applications because of their high-temperature performance, including excellent corrosion and creep resistance. Although Ni-based superalloys have traditionally been processed by casting, the use of additive manufacturing (AM) enables complex designs and/or near-net shapes to be produced. In Laser Powder Bed Fusion (LPBF), layers of powder are sequentially deposited on top of previously melted layers fused together by a laser beam. To understand microstructure development with processing, it is essential to understand the laser-material interactions during melting and solidification. In-situ synchrotron x-ray imaging of spot melting during simulated LPBF of Inconel 738 with different laser powers was performed at the Advanced Photon Source at Argonne National Laboratory. Solid-liquid interface velocities were directly measured and thermal gradients were modeled. Ex-situ characterization of the solidification microstructures was also performed to understand solidification of these alloys with processing variations.
8:40 AM
The Competition of Failure Modes in an Additively Manufactured Disk Superalloy: Tim Gabb1; C. Sudbrack2; M. Kirka3; S. Semiatin4; T. Smith1; C. Kantzos1; 1NASA Glenn Research Center; 2National Energy Technology Laboratory; 3Oak Ridge National Laboratory; 4Air Force Research Laboratory (retired)
Additive manufacturing of powder metallurgy disk superalloys can produce unique microstructures that are different from those usually encountered in traditional processing by consolidation, forging, and heat treatments. Unusual variations in grain size, major and minor phase precipitate sizes, and defects can occur. The associated failure modes of these unique microstructures are of high interest. The objective of this study was to compare the failure modes for a powder metallurgy disk superalloy LSHR produced by electron beam melting additive manufacturing. Specimens were subsequently given different solution heat treatments and a fixed aging heat treatment. Tensile, creep, and fatigue failure modes were screened in tests at elevated temperatures. Failure modes were considered with respect to these unique microstructures.
9:00 AM
Effect of Hot Isostatic Pressing on Mechanical Properties of Additively Manufactured Ni-based Superalloy Rene65: Colleen Hilla1; Andrew Wessman2; Michael Eff3; Ron Aman3; Michael Mills1; Wei Zhang1; 1Ohio State University; 2University of Arizona ; 3Edison Welding Institute
Additive manufacturing is widely used in aerospace applications as it allows for cost-effective production of complex geometries and low volume parts. These demanding applications require the printed alloys to possess superior high temperature strength and creep behavior. This study evaluates the effect of hot isostatic pressing (HIP) on the mechanical properties of additively manufactured Rene65, a high γ’ strengthened Ni-based superalloy. As-built, solution heat treated (SHT) and wrought samples were tested for comparison. For SHT and HIP, subsolvus and supersolvus conditions were analyzed. A unique HIP treatment was performed at low (subsolvus) temperature compensated with high pressure. Moreover, rapid controlled cooling was utilized to control precipitation. Compression and tension creep and elevated and room temperature tensile strengths were analyzed. Microstructures were characterized through electron backscattered diffraction and scanning electron microscopy. Improved mechanical properties were seen after HIP and multiple heat treatments of additively manufactured material, superior to wrought Rene65.
9:20 AM
Superalloy IN625 as a Candidate for Additively Manufactured Injectors for Hydrogen Combustion in Power Generation: Chantal Sudbrack1; Kyle Rozman1; Kristin Tippey1; Martin Detrois1; Lucas Teeter1; Matthew Searle1; Ömer Doğan1; 1National Energy Technology Laboratory
One key challenge for use of hydrogen fuels as an alternative to natural gas in industrial gas turbines is combustor performance, in particular the fuel injectors, where additive manufacturing enables design flexibility for performance optimization at potentially lower production costs. Both solid solution and precipitate strengthened Ni-based superalloys manufactured by laser powder bed fusion (L-PBF) are under evaluation for candidate down-selection using elevated temperature tensile, creep, low cycle fatigue and hydrogen embrittlement testing. The processing parameters used for the first candidate, superalloy IN625, produced dense parts (porosity <0.04%) for which HIP heat treatment was unnecessary. Solutioning the L-PBF IN625 yielded an equiaxed grain structure with sparsely distributed micron-sized MC carbides. The room and elevated temperature tensile properties were comparable to conventional IN625, and differences mostly correlated to grain size. The mechanical testing and hydrogen embrittlement results are presented and discussed in context of microstructural observations, failure mechanisms, and property requirements.
9:40 AM
Nitride Formation and Their Influence on Delta Phase Precipitation in Additively Manufactured Nickel Superalloys: James Zuback1; Selda Nayir2; Mingze Gao2; Todd Palmer2; 1National Institute of Standards and Technology; 2Pennsylvania State University
Elemental segregation is well-known to accelerate the nucleation and growth of delta phase in rapidly solidified nickel superalloys containing niobium. Here, delta phase formation is probed in two additively manufactured Inconel 625 alloys containing high levels of nitrogen and variations in minor alloying elements. Changes in secondary phase formation in as-deposited alloys and after hot isostatic pressing led to strikingly different responses to prolonged exposure at 870 °C. These differences are linked to existing secondary phases, since each type of precipitate contains varying levels of niobium needed for delta phase formation. One alloy with primarily titanium-rich nitrides precipitated delta phase within minutes that grew to a volume fraction of approximately 15 % after 10 hours. In contrast, negligible quantities were detected after 10 hours in the other alloy containing a variety of niobium-rich nitrides. Hot isostatic pressing was found to retard delta precipitation in both alloys up to 100 hours.
10:00 AM Break
10:20 AM
AM Processing and Microstructural Evolution in Nickel-based Superalloys: Ruben Ochoa1; Amy Clarke1; 1Colorado School of Mines
Metal additive manufacturing (AM) has shown promise in producing parts while reducing cost, waste, and increasing geometric complexities over parts produced by conventional manufacturing. A major drawback of AM is the lack of understanding of microstructural evolution and control during the build process, especially during rapid solidification. Local thermal conditions within AM parts favor the formation of columnar grains, which may lead to hot cracking and anisotropy. Thus, understanding the columnar-to-equiaxed transitions relative to AM processing conditions is crucial to control microstructure development. This work focuses on exploring the relationship between AM processing conditions and history on microstructural evolution in nickel-based superalloys.
10:40 AM
A Compositional and Microstructural Understanding of Powder-blown Directed Energy Deposition (DED) Used for Functionally Graded Ni-superalloys Alloys for Hot-and-harsh Gas Path Environments: Marissa Brennan1; Chen Shen1; Shenyan Huang1; Michael Knussman1; Daniel Ruscitto1; Alex Kitt2; Changjie Sun1; Lee Kerwin2; Anindya Bhaduri1; Siyeong Ju1; Hyeyun Song2; Lang Yuan3; 1GE Research; 2EWI; 3University of South Carolina
Powder-blown directed energy deposition (DED) enables parts to be processed with unique composition and properties tailored for specific performance needs. In particular, the layer-by-layer technique may be fine-tuned to create functionally graded material (FGM) structures. FGMs are advantageous for eliminating sharp interfaces inherent of welding of two or more components together, reducing coefficient of thermal expansion (CTE) induced residual stresses, while subsequently lowering the cost by using hybrid materials. FGM path design is intended to minimize undesirable phase formation inherent of hot-and-harsh gas path (HGP) environments which reduce the life of components. This study elaborates on the manufacturing and characterization (i.e. EBSD, SEM/EDS, EPMA, and hardness) of compositionally grade IN718/R41 (low γ’ to medium γ’) strengthened Ni-based superalloy FGMs processed by powder-blown DED. Compositional and microstructural evidence provided input for machine learning (ML) algorithms for further development and predictions of process parameters for printing FGM structures.
11:00 AM
Directed Energy Deposition of Bi-metallic Tensile Specimens by Direct Bonding of Inconel 625 to Stainless Steel 304: Anthony Stair1; Nicholas Jones1; Jack Beuth1; Maarten de Boer1; 1Carnegie Mellon University
Bonding dissimilar metals by Additive Manufacturing (AM) can create structures with complex geometries and tailored material properties. Bonding can be difficult due to the formation of unintended intermetallic phases that may form, or due to stresses on the part caused by large differences in thermal expansion coefficients. In this work, by direct bonding Inconel 625 powder feedstock to a stainless steel 304 plate using directed energy deposition (DED), we have successfully avoided gross defects such as voids, cracks and deleterious phases in single beads and single-layer pads. CALPHAD simulations have guided the choice of process parameters needed to avoid the formation of intermetallics. Bi-metallic tensile specimens have been printed out-of-plane with an Inconel 625 to stainless steel 304 joint located within the gage section. Strength results will be presented to evaluate the bond quality of the tailored bimaterial joint.
11:20 AM
Multi-material Additive Manufacturing with Inconel 718 and GRCop-84: Nicholas Obrien1; Zexiao Wang1; Nicholas Jones1; Sheng Shen1; Jack Beuth1; 1Carnegie Mellon University
Additive Manufacturing (AM) has enabled the production of many new metal composites that are directly bonded to one another, allowing for continuous changes in material properties across their interface. Inconel 718 is a commercially available nickel alloy with high strength properties but low thermal conductivity. GRCop-84 is a thermally conductive copper alloy that can compensate for Inconel’s low conductivity. In this work, these two alloys are bonded together in a layered fashion to test the feasibility of forming a high-strength, high-conductivity composite material. Equilibrium phase simulations have suggested the presence of brittle intermetallic phases within the bond, so the benefits of a pure nickel interlayer are also studied. Energy Dispersive X-Ray Spectroscopy (EDS) is used to quantify the presence of different phases in the bond.