Transportation Energy Conversion

The National Energy Technology Laboratory (NETL) will develop lightweight, cost-effective, precipitation-strengthened refractory high entropy alloys (RHEAs) for additive manufacturing. The advantage is an alloy with all phases in thermodynamic equilibrium, promoting high microstructural stability. The alloys will be comprised of a ductile high entropy solid solution matrix strengthened by fine precipitates of the high entropy carbides. NETL will use high throughput, multi-scale computer modeling, and machine learning to identify novel alloys within the large compositional space.

Current alloys used in gas turbines operate at about 90% of their melting temperature, which sets a limit on achieving higher temperatures. Refractory metal alloys (RMA) have the capability to enable continuous operation at 1300°C and with compatible coatings along with cooling systems to allow for gas inlet temperatures to reach 1800°C. The high RMA melting temperatures present challenges for traditional manufacturing methods, however.

The Zero-carbon Ammonia-Powered Turboelectric (ZAPTurbo) Propulsion System is a very high efficiency and lightweight turboelectric system that uses green ammonia as a fuel and coolant via regenerative cooling. Coke-free heating of this carbon-free ammonia fuel enables a high level of waste-heat recovery that will be used for the endothermic cracking of ammonia prior to its combustion, significantly increasing the cycle efficiency. The proposed propulsion system includes an efficient AC electric powertrain for turboelectric cruise, with battery boost for takeoff and climb flight phases.

Increasing the efficiency of power generation and air transportation can only be achieved by increasing the temperature at which generation/propulsion turbines operate. The emerging Refractory High Entropy Alloys (RHEAs) can enable much higher operating temperatures than the state-of-the-art. Identifying the alloys' chemistry is difficult due to the vastness of the RHEA chemical space.

The University of Maryland will leverage a newly invented, ultrafast high-temperature sintering (UHS) method to perform fast exploration of new environmental-thermal barrier coatings (ETBCs) for 1300°C-capable refractory alloys for harsh turbine environments. UHS enables ultrafast synthesis of high-melting oxide coatings, including multilayers, in less than a minute, enabling rapid evaluation of novel coating compositions.

The drive for higher fuel efficiency and higher core power of gas turbines used in electric power generation and aircraft propulsion requires higher peak operation temperatures in the hottest sections. Current state-of-the-art refractory metal alloys (RMAs), although highly resistant to heat and wear, tend to oxidize in the gas turbine environment.

Raytheon Technologies Research Center (RTRC) aims to design and validate the manufacturability and mechanical properties of a new hot section turbine alloy. To achieve higher efficiency turbine operation, RTRC will use additive manufacturing (AM) to produce test coupons (specimens) and potentially a representative turbine blade using a high entropy alloy (HEA) enhanced with oxide dispersion strengthening (ODS) particles.

Massachusetts Institute of Technology will develop a new additive manufacturing (AM) process, capable of producing refractory composite materials for use in high-temperature, oxidation-resistant turbine blades and other demanding energy-conversion applications. The AM process will incorporate hardware and software to establish uniform, high-quality refractory materials that are traditionally prone to micro-cracking and oxidation during AM, thereby establishing the required mechanical properties and oxidation resistance of a target alloy.

The University of Utah will use physical metallurgy principles and artificial intelligence to identify the chemistry of new niobium (Nb)-based refractory alloys to ensure they have excellent high-temperature properties without being brittle at low temperatures. The artificial intelligence approach will discover promising compositions for the new alloys based on existing knowledge of simple alloys. The computational materials models will be used to predict the proper processing conditions for the material chemistries.

Current Ni-based alloys used in turbine blade applications operate at 1100°C. This project seeks to develop two classes (Ni) alloys that can continuously operate at 1300°C with coatings, enabling gas turbine inlets of 1800°C or higher. Temperature increases can be achieved through the use of refractory alloys, including molybdenum, niobium, tungsten, and tantalum. Oak Ridge National Laboratory (ORNL) will provide data on alloys and coatings developed by ULTIMATE teams.