Optimising the design of additive manufacturing alloys
Europe’s manufacturing industry faces ongoing challenges from global competition and a shift towards resource and energy efficiency. New oxide-dispersoid strengthened (ODS) metallic materials could bring major advances for the European process industry, through the creation of sensor-integrated, high-temperature devices such as gas burner heads and heat exchangers. In the EU-funded topAM(opens in new window) project, a research consortium aimed to develop new processing routes for creating ODS materials on a basis of various metals dispersed with nano-sized oxide and nitride particles. The project aimed to offer new nanostructured metallic materials, which can be built into complex-shaped structures using 3D printing, i.e. laser-beam powder bed fusion (PBF-LB/M). “The developed ODS alloys can be used in highly carburising and oxidising atmospheres of up to 1 400 °C operating temperatures, for example in syngas plants for the production of hydrogen,” says Ulrich Krupp(opens in new window), professor and chair of Materials Engineering of Metals at the IHEK Steel Institute, RWTH Aachen University. “This was proven in a gas burner test using a 3D-printed Ni-base strengthened superalloy.” The research could help not only manufacturing industries, but also the development of large-scale and clean power plants. Many of the leading technologies in power generation rely on the safe and efficient use of high-temperature materials and devices.
Integrating computational engineering into ODS production
To improve the ODS production process, the team used an integrated computational materials engineering (ICME)-guided developing route. This involved using computational thermodynamics to predict the occurrence of the various phases within the complex alloys, depending on their individual chemical composition. “In a next step, we were using models to predict the creep life of the alloys depending on the size and volume fraction of ODS particles,” explains Krupp. This allowed the team to simulate the required concentration of the particle-forming alloying element.
Improving powder modification through nanoparticles
topAM started with a variety of potential powder modification routes to integrate nanoparticles into the production process. This research found that internal nitridation processes yielded the best results. During gas atomisation – atomising the liquid alloy by a high-pressure mixture of argon and nitrogen – the small titanium concentration in the alloy droplets is able to react with the nitrogen gas stream in situ. “A similar result was obtained by exposing the alloy powder to a nitriding atmosphere of a fluidised bed reactor ex situ,” notes Krupp, topAM project coordinator. High-resolution electron microscopy showed the nano-sized titanium nitride particles to be evenly distributed. “The 3D-printed samples using the respective ODS powder showed superior mechanical properties, in particular at high temperatures,” says Krupp. The ICME-guided ODS alloy development and the powder modification by means of the fluidised bed reactor are already the subject of patent applications, and follow-up projects have been initiated. This includes in different fields of application, such as aerospace applications and high-voltage switches.
Boosting Europe’s manufacturing capabilities
ODS alloys provide unique combinations of strength, creep and corrosion resistance at very high temperatures, while 3D-printing by powder bed fusion allows a highly individualised design. “This fulfils structural and functional requirements of demanding products, such as those used in aerospace applications and energy technologies,” adds Krupp. “Process industry and high-efficient cooling units in large-scale microelectronics can also be realised to maintain Europe’s competitiveness and independence in growing and strategic market segments.”
