Superalloy 718 and Derivatives: Additive: Powder & Processing
Program Organizers: Joel Andersson, University West; Chantal Sudbrack, National Energy Technology Laboratory; Eric Ott, GE Additive; Zhongnan Bi, Central Iron and Steel Research Institute
Tuesday 2:55 PM
May 16, 2023
Room: Admiral
Location: Sheraton Pittsburgh Hotel at Station Square
Session Chair: Timothy Smith, NASA Glenn Research Center; Kevin Bockenstedt, ATI Specialty Materials
2:55 PM Invited
Surface Roughness of Additively Manufactured IN718 & H282 Superalloys from Multi-size and Multi-laser Machines: Ramesh Subramanian1; K Cwiok1; Anand Kulkarni1; 1Siemens Corporation
Laser Powder Bed Fusion (LPBF) of metallic components is unlocking new design options for high efficiency gas turbine component designs not possible by conventional manufacturing technologies. Surface roughness is a key characteristic of LPBF components that impacts heat transfer correlations and crack initiation from co-located surface defects - both are critical for gas turbine component durability and performance. However, even for a single material, there is an increasing diversity in laser machines (single vs multi-laser), layer thicknesses (~20-80 microns) and orientations to the build plate (upskin, vertical and downskin) that result in significant variability in surface roughness. Build direction effects are particularly important when considering three-dimensional gas turbine components each having unique cooling features. This study systematically compares the external and internal surface roughness of two gas turbine superalloys - Inconel 718 and Haynes 282 - from multi-laser and multi-size machines. This presented data will be discussed in detail, to show potential applicability of a 3D process signature surface across machines and substrate orientations for additively manufactured superalloys.
3:25 PM
Effects of Scan Strategy Induced Microstructural Differences on Thin-wall SLM IN718 Fatigue Performance: Connor Varney1; Imran Noor1; Paul Rottmann1; 1University of Kentucky
The as-printed microstructure of additively manufactured parts is a function of many variables that span from scan strategy to part geometry. This is particularly relevant in precipitation strengthened alloys (e.g. IN718), as thermal history—which itself varies across a build—dictates the distribution of precipitates in the microstructure. Elucidation of the complex relationship between geometry, scan strategy, and resultant microstructure is necessary to optimize scan strategies. In this study a series of IN718 compact tension fatigue test samples were printed via selective laser melting at 1.25mm in thickness using a contour+hatching scan strategy with both rotating and static beam directions at each build layer with half having the crack oriented parallel and the others perpendicular to the build direction. To quantify the effect of sub-surface porosity on fatigue crack initiation, a selection of the samples had an internal (~0.5mm) pore placed in front of the notch. To investigate the influence of scan strategy on the low-cycle fatigue (LCF) resistance of AM IN718, these samples were LCF tested to failure using a custom micromechanical test setup equipped with piezo actuator and digital image correlation (DIC) to identify the onset of plasticity and the initiation and propagation of fatigue cracks and across sample surfaces. The driving hypothesis for this study is that the rotated scan strategy increases the fatigue resistance due to a more uniform microstructure with smaller grains. As-printed defects and microstructural features were characterized utilizing several techniques (SEM, EBSD, microCT) and compared to observations from mechanical testing.
3:45 PM
Characterization of Laser Powder Bed Fusion of Nickel Based Superalloy Haynes 282: Kameshwaran Swaminathan1; Jonas Olsson1; Tahira Raza1; Joel Andersson1; Peter Harlin1; 1University West
Nickel based superalloy Haynes 282 cubes were manufactured using Laser powder bed fusion process with powder layer thickness of 60 and 90 microns to study the effect of Laser Power, Laser Scan Speed and Hatch distance on the melt pool dimensions and porosity. The melt pool dimensions, and porosity were measured at the center of the cubes parallel to the build direction. Variation of melt pool depth and overlap exist within the same cube signifying the scatter present in the process. Laser scan speed was found to be the most significant parameter for porosity and Hatch distance was found to be the most significant parameter affecting the average melt pool overlap depth in the cubes built with 60 microns layer thickness. Interaction of speed and hatch distance was found to be the most significant parameter for porosity and Laser scan speed was the most significant parameter for average melt pool overlap depth in cubes built with 90 microns layer thickness. Comparison of measured responses with individual parameters provide partial trends of melt pool dimensions and porosity. A better trend of the melt pool dimensions and a marginal trend of porosity is obtained on comparison with line and area energy densities. Ratio of maximum length to minimum length of a defect is measured to determine the shape of the defects and averaged to provide insight into the dominant shape of defect for a given set of parameters.
4:05 PM
Investigating the Influence of Build Parameters and Porosity on Fatigue of AM IN718: Alexander Caputo1; Rick Neu1; Xiayun Zhao2; Chaitanya Vallabh2; Haolin Zhang2; 1Georgia Institute of Technology; 2University of Pittsburgh
Using laser powder bed fusion additive manufacturing a series of 10 walls along with two turbine blades were made, sectioned into fatigue specimens, and tested using high cycle fatigue testing with a stress ratio of 0.1 at 538℃. Each wall was built with different parameters to explore the effects of different laser-material interaction modes (conduction, transition, keyhole) on the effect of the internal porosity and microstructure of AM IN718 as well as the subsequent fatigue properties. The internal porosity in the full gage regions of all fatigue specimens was characterized prior to testing using X-ray computed tomography. Following fatigue testing, SEM fractography was used to identify the location of the fatigue critical flaw that led to failure. Using the XCT porosity data and fatigue test results, and critical flaw locations, a machine learning model was trained to predict fatigue performance of IN718 at high temperature given information on build parameters and non-destructively collected XCT porosity data.
4:25 PM
(LBN - P5) Phase Evolution and Tensile Deformation of IN718-René41 Graded Superalloy Fabricated by Directed Energy Deposition: Shenyan Huang1; Ke An2; Chen Shen1; Changjie Sun1; Alex Kitt3; 1GE Research; 2Oak Ridge National Lab; 3Edison Welding Institute
A compositionally graded material comprised IN718 and René41 (a medium gamma prime superalloy) was fabricated using laser blown-powder directed energy deposition (DED/LB-M). Hot gas path components that require high and low temperature capabilities at different locations may benefit from such graded superalloy, potentially eliminating the use of welded or mechanically joined components. In-situ neutron diffraction experiment coupled with heating/cooling was performed to understand phase evolution up to 1150°C in as-built specimen. A decreasing lattice spacing from IN718 to René41 was observed over the temperature range. Linear expansion and average coefficient of thermal expansion calculated from neutron data upon cooling showed consistency with model prediction. Fraction and solvus temperature of gamma prime increased with compositions approaching René41. In addition, in-situ tensile loading experiment at 650°C was performed to investigate elastic, plastic deformation behavior within the graded composition at grain and phase levels. Diffraction elastic constants and Poisson’s ratios showed small difference between as-built and heat-treated specimens and between gamma and gamma prime phases. The applied heat treatment significantly improved grain-level yield stress for IN718 rich compositions, while small improvement was observed in R41 rich compositions. These results provide insights into optimization of graded superalloy and crucial data for modeling material behavior.
4:45 PM
(LBN - P6) Exploring High Temperature Fretting Wear Behaviour in Wrought and Additively Manufactured DA-718 Superalloy: Sathisha CH1; Kesavan D2; Sridhar MR1; Arivu Y2; 1GE Rerearch; 2Indian Institute of Technology
The occurrence of fretting wear is due to the small oscillatory motion of two contacting surfaces under gross-contact pressure. Further, wear mechanisms are dependent on the material's response to these contact conditions. Elevated temperature plays a significant role in determining material performance and changes the wear regime. This research explores the fretting wear behaviour of DA-718 nickel-based superalloys made through both wrought and Laser Powder Bed Fusion (LPBF) additive manufacturing methods. Gross-slip fretting wear tests were conducted at constant high contact pressure and elevated temperature, and the wear behaviour of the two alloys was compared using a custom-built fretting test setup to simulate fretting wear. The results indicate that the additively manufactured DA-718 had similar wear behaviour to the wrought DA-718, but with a higher degree of variation attributed to microstructure-dependent wear phenomena. The microstructure of the alloys was also analyzed to understand the mechanisms governing wear behaviour. These findings have significant implications for the use of additively manufactured DA-718 in high-contact pressure and high-temperature applications, such as gas turbine engines.
5:05 PM
Influence of Morphology and Size Distribution of Haynes 230 Particles on the Powder Spreading Behavior and Performance on Selective Laser Melting: Peng Zhang1; Rui Wang1; Shaoming Zhang1; Zhongnan Bi1; Xizhen Chen1; Hailong Qin1; Guangbao Sun1; 1Central Iron And Steel Research Institute
There is increasing interest in the use of additive manufacturing (AM) for superalloys due to their broad applications in the aerospace industry. As the raw materials, high-quality metal powder is very important for successful selective laser melting in AM. In this work, Haynes 230 powders manufactured by VIGA and PREP were characterized and compared. Results demonstrated P-230 powder is superior to V-230 powders. P-230 powder exhibits the lower Hausner ratio and better flowability. Meanwhile, attributed to superior sphericity and fewer satellite particles, lower dynamic angle of repose and cohesive index were achieved by P-230 powder, which means better dynamic flow and spreading of the powder during the recoating process of selective laser melting (SLM). In terms of their performance on SLM, the powder bed density of the P-230 powder is higher, and samples prepared with P-230 powder exhibited higher relative density. Although both V-230 and P-230 samples were all HIPed at 1200℃ for 4h, P-230 samples revealed much higher yield strength at room temperature.