Economical, On-Demand GRCop Alloy Production

NASA's new Ni-based superalloy uses a powder metallurgy (PM) composition that inhibits the deleterious gamma-prime to gamma-phase transformation along stacking faults during high temperature creep deformation. Ni-base superalloys have excellent high temperature properties, mostly due to the presence of coherent precipitates. At higher temperatures, these precipitates are defeated by the diffusional shear dislocations producing intrinsic and extrinsic faults. Recent studies have found that, during deformation of turbine disk alloys at high temperature, Co, Cr, and Mo segregate to these faults (removing Ni and Al) inside the strengthening precipitates of these alloys. This represents a local phase transformation from the strengthening precipitate to the weaker matrix phase. Therefore, this elemental segregation significantly weakens the ability of a precipitate to withstand further deformation, producing faster strain rates in the alloy at higher temperatures. This invention presents a solution to prevent this type of segregation along these two faults to improve the creep properties of turbine disks and similar Ni-based alloys. By alloying a specific amount of eta phase formers (Ti, Ta, Nb, and Hf), the phase transformation to can be eliminated along 2-layer extrinsic stacking faults (SESFs) in precipitates without precipitating bulk eta phase. Also, by adding a certain amount of D019 formers (Mo and W), the phase transformation to can be mitigated along 1-layer intrinsic stacking faults (SISFs) without producing bulk sigma phase. This alloy composition incorporates both strengthening methods for use in jet turbine disks, though the composition has applications in other high-stress and/or high-temperature environments as are found in power plants, space launch systems, and other critical structural applications.

In order to improve the properties of monolithic metallic materials, alloying additions are made that create secondary phases and/or precipitate structures. These improvements must occur during melt solidification and are governed by the thermodynamics of the process. That is, optimizing the metallic alloy is possible only as much as thermodynamics allow. Developing novel methods to combine metallic compositions/alloys into a fully dense material is of interest to create materials with novel property combinations not available with monolithic alloys.While various approaches for layering two-dimensional materials exist, their capabilities are typically limited and non-isotropic. Further, while three-dimensional composites may be formed with conventional powder metallurgy processes, it is generally very difficult to control the arrangement of the phases, for example due to randomness created by mixing powders. This invention is method for creating a multiple alloy composite structures by forming a three-dimensional arrangement of a first alloy composition, in which the three-dimensional arrangement has a substantially open and continuous porosity. The three-dimensional arrangement of the first alloy composition is infused with at least a second alloy composition. The three-dimensional arrangement is then consolidated into a fully dense solid structure.

SMAs are important multifunctional materials for the development of adaptive engineering structures. They exhibit a high work output that is competitive with, or superior to, conventional hydraulic, pneumatic, or electromagnetic actuators. While highly promising, SMAs are not always a practical alternative to conventional actuators because of their limited phase transformation temperatures and dimensional instability. Thanks to Glenn's innovative new SMA, that's about to change. Unlike traditional binary NiTi SMAs, Glenn's Ni-Ti-Hf-Zr SMA includes secondary, nanoscale precipitate phases that offer inherent dimensional stability to the material. Consequently, there is minimal to no need for training, resulting in much faster production times, lower processing costs, and a finished product with superior work outputs and better operational life. These Ni-rich alloys can be produced by Vacuum Induction Melting, Vacuum Arc Melting, Vacuum Arc Remelting, and Induction Skull Melting. Perhaps the most exciting characteristic of Glenn's SMA, however, is its ability to achieve a broad range of transformation temperatures suitable for high temperature (100 to 300°C), ambient, and sub-ambient temperature applications nearing -100°C. Furthermore, these temperatures can be tailored and fine-tuned though heat treatment to fit the needed parameters for the application of interest. In contrast, traditional NiTi SMAs exhibit fixed phase transformation at temperatures from slightly below room temperature to around 100°C. Glenn's Ni-Ti-Hf-Zr SMA opens the door to countless applications that can benefit from the unique properties of SMAs but require high durability and extreme temperature capability.

Shape memory alloys (SMAs) are metals that can return to their original shape following thermal input and are largely used as actuators for various applications across industries including space, aeronautics, automotive, and biomedical. These alloys can require long processing times to stabilize through repeated training cycles and suffer from loss of strength and stability during use. Precipitation strengthening (using heat treatments to grow small nanoscale regions of distinct metal phases within the base alloy) is one way to mitigate these issues. The NASA inventors have combined a modification of typical NiTi compositions by introducing Palladium (Pd) and small amounts of other metals and specific heat treatments to produce a novel SMA with improved properties. Specifically, the alloy is inherently stable, reducing both the need for extended processing times to stabilize the metal and the possibility of failure during high numbers of actuation cycles. Further, the SMA is specifically designed to have significantly lower hysteresis (the temperature difference between the heating and cooling) than current state of the art SMAs, i.e., at or below 10°C compared to 20°C or above. These properties combine for a SMA with enhanced properties usable across various industries and applications for reliable actuation. The related patent is now available to license. Please note that NASA does not manufacturer products itself for commercial sale.

NASA's technology is the first successful 3D-printing of high temperature carbon fiber filled thermoset polyimide composites. Selective Laser Sintering (SLS) of carbon-filled RTM370 is followed by post-curing to achieve higher temperature capability, resulting in a composite part with a glass transition temperature of 370 °C. SLS typically uses thermoplastic polymeric powders and the resultant parts have a useful temperature range of 150-185 °C, while often being weaker compared to traditionally processed materials. Recently, higher temperature thermoplastics have been manufactured into 3D parts by high temperature SLS that requires a melting temperature of 380 °C, but the usable temperature range for these parts is still under 200 °C. NASA's thermoset polyimide composites are melt-processable between 150-240 °C, allowing the use of regular SLS machines. The resultant parts are subsequently post-cured using multi-step cycles that slowly heat the material to slightly below its glass transition temperature, while avoiding dimensional change during the process. This invention will greatly benefit aerospace companies in the production of parts with complex geometry for engine components requiring over 300 °C applications, while having a wealth of other potential applications including, but not limited to, printing legacy parts for military aircraft and producing components for high performance electric cars.