In the aerospace field, high-temperature alloy materials are used to manufacture components in key areas of jet turbine engines, such as combustion chambers, high- and low-pressure turbine areas, and compressor rear ends. All parts in these areas are exposed to high temperatures and higher levels of oxidation.
Powder bed laser melting (L-PBF) metal 3D printing technology is highly valued in the manufacture of high-value-added function integrated high-temperature alloy parts, especially in the manufacture of high-temperature alloy parts with integrated advanced cooling structure due to its advantages in the manufacture of complex structures. The field has played a role that traditional technology cannot play. In addition, high-temperature engine components are usually very expensive. The L-PBF process can reduce material waste and shorten the lead time, allowing manufacturers to benefit from inventory management. However, there are still challenges for L-PBF in the additive manufacturing of superalloys. For example, due to the strong temperature gradient, the metastable chemical, structural, and mechanical states are caused, which causes metallurgical defects that affect performance.
Nickel-based alloys are high-temperature alloy materials commonly used in traditional manufacturing processes, such as IN738, IN713 and MarM247. However, due to the chemical properties of traditional nickel-based superalloy materials are not compatible with laser melting 3D printing technology, because they cannot respond well to rapid thermal gradient changes, and it is practically impossible to control the amount of cracking during welding. Therefore, these alloy materials are mostly processed by casting methods with relatively low cooling rates.
If aerospace manufacturing users want to use L-PBF 3D printing technology to enhance the competitive advantage of high-temperature applications, finding a superalloy material specifically suitable for this 3D printing technology without compromising structural integrity becomes a key part. According to market observations from 3D Science Valley, Honeywell’s testing of a new nickel-based superalloy material-ABD-900AM is precisely promoting the application of additive manufacturing of superalloys.
Materials optimized for additive manufacturing
High crack resistance and high density
ABD-900AM is a nickel-based superalloy material developed by Alloyed for powder bed laser melting 3D printing technology, which is used for the additive manufacturing of high-strength and/or medium creeping components. The static strength is close to that of cast IN-713C. The material is optimized for the following points:
optimization
• Strength at 900°C • Resistance to strain and solidification cracks • Resistance to oxidation
The additive manufacturing applications of ABD-900AM include: static aerospace engine parts, heat exchangers, and components with internal cooling requirements.
According to the technical data of Alloyed, the performance evaluation of ABD-900AM material by using L-PBF 3D printing technology shows that compared with the alloys commonly used in additive manufacturing, ABD-900AM has higher strength and manufacturability, and shows High crack resistance and 99.9% density.
The mechanical properties of ABD-900AM and 718 alloy were compared. When the temperature is higher than 800 degrees Celsius, the yield stress of ABD-900AM is increased by at least 30%, and the creep temperature capability is increased by up to 100 degrees Celsius.
Multi-dimensional testing from material to process
Honeywell conducted a series of tests to confirm and optimize the performance of the alloy, and obtained some very positive results. The test starts from the following points.
l Manufacturability
The focus is to evaluate the alloy performance of ABD-900AM nickel-based superalloy material during L-PBF additive manufacturing, and whether the thermal gradient generated during this process will damage the integrity of the final part. Honeywell tried various test geometries in the German EOS metal 3D printing system, and carried out a component scale test, and found that there was no deformation caused by cracks under the printing conditions, and the tested parts had good surface finish.
l Powder recyclability
When considering the economics of using metal additive manufacturing processes, the ability to reuse molten powder is an important factor. Honeywell tested the recycled powder, and compared with the new powder, the performance of the parts made from the recycled powder did not change significantly.
l Post-processing capabilities
3D printed parts usually require post-processing, and the post-processing process may affect the mechanical properties of the material, thereby affecting the function of the part. Vacuum heat treatment and hot isostatic pressing (HIP) are often used to eliminate internal voids in metal 3D printed parts. Honeywell has also conducted corresponding tests. No welding is found on the post-processed ABD-900AM material 3D printed parts. After" cracks.
l Tensile test
Honeywell conducted the ASTM standard tensile test to measure the tensile strength, breaking strength, maximum elongation, and area reduction between 427°C and 927°C in two construction directions. The test shows that the test points have good repeatability, and the high temperature strength of the ABD-900AM material is comparable to that of traditional cast nickel alloys.
l Low cycle fatigue test
Low-cycle fatigue (LCF) is a low-cycle durability test in which components are subjected to mechanical cyclic plastic strain, resulting in fatigue failure in a short period of time. Honeywell conducted a low-cycle fatigue test on ABD-900AM material at 650°C. The results show that the parts of ABD-900AM material that have not undergone hot isostatic pressing have better performance than the 718 alloy that has undergone hot isostatic pressing. Performance.
The results of the work between Honeywell and Alloyed show that ABD-900AM has good welding and melting properties. Although the ABD900AM material cannot replace the CM Mar-247 material for casting due to its oxidation properties in most cases, it does have very good mechanical properties at high temperatures compared to Mar 247, IN792, IN713 or IN738.
Nickel-based superalloy 3D printing has formed an "indissoluble bond" with the manufacturing of next-generation aerospace engines and gas turbines. The performance of high-temperature parts of the engine has been improved by changing the design and manufacturing logic.
Integrated leaf disc
In the field of research and development, the international R&D member of the ACAM-Aachen Additive Manufacturing Center, a turbomachinery expert from the RWTH Aachen University Digital Additive Production DAP, and Fraunhofer Fraunhofer Institute of Production Technology IPT cooperated. Integrated blisk made of nickel The researchers successfully developed the L-PBF 3D printing manufacturing process for the blisk, and also applied the lattice lattice structure to support the components during the construction process, which significantly reduced the material that needs to be removed later. And avoid the vibration in the milling process.
Nickel-based super alloy IN 718 blade integrated disc
Burner
Honeywell disclosed the details of the development of a double-walled burner through 3D printing technology in the newly obtained patent. Unlike the conventional double-wall structure, the double-wall structure developed by Honeywell combines impingement cooling and jet cooling into a single structure. It is used to conduct heat from the thermal side wall and reduce the thermal gradient, thereby reducing the plane stress. This design also provides the smallest footprint and potentially reduces weight compared to traditional double-walled structures.
The double-wall structure 300 (the first wall, the second wall and the base) in the figure is an integrated structure, which is manufactured by the selective laser melting additive manufacturing process. The double-wall structure is manufactured by nickel-based superalloys, which can form impact cooling The hole 308 and spray cooling channel 312 are followed by a coating and or thermal barrier coating.
Heat exchanger
L-PBF 3D printing technology is still spawning the development of next-generation heat exchangers. In 2019, GE announced that it will cooperate with the University of Maryland and Oak Ridge National Laboratory to develop UPHEAT ultra-high-performance heat exchangers. The development plan will be completed within two and a half years. More efficient energy conversion and lower emissions. GE hopes that the new heat exchanger will operate at temperatures exceeding 900°C and pressures above 250 bar, and the thermal efficiency of the supercritical CO2 power cycle will increase by 4%, which will increase power output while reducing emissions. In terms of materials, this new type of heat exchanger will use a unique high-temperature, crack-resistant nickel-based superalloy, which is a material designed by the GE research team for the additive manufacturing process. The heat exchanger includes multiple additive manufacturing methods that make the fluid channel smaller in size, have a thinner wall to form a fluid path, and have an intricate shape. These heat exchangers cannot be manufactured using previous traditional manufacturing methods.
Function integrated core machine
Turbines manufacturing company Sierra Turbines proposed design optimization goals for micro-turbines and achieved these goals through L-PBF 3D printing technology.
By using the metal additive manufacturing (AM) technology of the manufacturer VELO3D, Sierra Turbines reduced the number of key components from 61 to one, and also obtained many important performance improvements. The 3D printing material used in this core machine is nickel super alloy, which is the material of choice for the combustion chamber of many large gas turbines. Additive manufacturing enables Sierra Turbines to obtain complex design features to improve thermal efficiency and obtain longer maintenance intervals, which is an unprecedented breakthrough.
Premixer
Siemens successfully reduced emissions for the SGT-A05 aeroderivative gas turbine, and achieved impressive results with a 3D printed dry low emission (DLE) premixer, showing that it can significantly reduce CO emissions. This achievement has further consolidated Siemens' world-leading innovative applications of additive manufacturing and its position in the energy sector.
Siemens' achievements in manufacturing this specific gas turbine component through 3D printing are remarkable. From concept to engine testing, development took only seven months, which is impressive for components that require such tight tolerances and work under high loads and temperatures. The DLE premixer is very complex, using traditional casting and CNC machining manufacturing methods involving more than 20 parts. By using Siemens qualified nickel-based super alloys as additive manufacturing materials, 3D printing pre-mixer components only require two components, and the lead time is reduced by about 70%.
The 3D printing of the DLE premixer enables Siemens to simplify the complexity of the production process, reduce external dependencies in the supply chain, and improve the geometry of the components to achieve better fuel-air mixing.
Manufacturing is the "fatal weakness" in the application of superalloys such as nickel-based superalloys. If there is no lengthy and expensive subtractive manufacturing through casting machining, it is impossible to obtain structurally good mechanical properties. 3D printing can effectively manufacture complex structures, which are usually difficult to achieve, such as blisks, internal components with integrated cooling channels, and lattice structures.
However, most conventional nickel-based superalloys cannot be used in the transition from precision casting process to 3D printing technology, because these materials are optimized for traditional processes such as casting. Due to the rapid repetitive thermal cycle of the 3D printing process, a new composition for 3D printing process parameters can be designed in a data-driven way of composition calculation, so as to adjust the microstructure and performance for the high cooling rate of additive manufacturing. Therefore, optimizing nickel-based superalloy materials for additive manufacturing processes, reducing their metallurgical defects, and introducing alloy materials suitable for 3D printing, play an important role in promoting the application of superalloy additive manufacturing.