NASA Glenn researchers developed a new oxide dispersion strengthened medium entropy alloy (ODS-MEA) via additive manufacturing (AM). ODS alloys, in which nanoscale ceramic particles are distributed within the metal, were originally developed to enhance mechanical properties (e.g., creep resistance, tensile strength, microstructure integrity) at extreme temperatures. Such alloys show promise for metal components of gas turbines, rocket engines, nuclear reactors, and other high-temperature applications; however, the conventional mechanical alloying process to produce such alloys is highly inefficient, time-consuming, and costly.
ODS-MEA is designed for production via selective laser melting. The alloy can be fabricated into complex geometries and is resistant to stress cracking and dendritic segregation. It is not susceptible to deleterious phase changes when exposed to extreme temperatures and requires limited post-processing.
The alloy maintains properties up to 1100 °C and is not susceptible to deleterious phase changes when exposed to extreme temperatures — an issue ubiquitous to Ni-based superalloys such as Inconel-625 and Inconel-718. Yttria particles are dispersed throughout the alloy to maximize strength and creep resistance at high temperatures using a novel fabrication technique. This technique employs an acoustic mixer to stir nanoscale yttria oxide powder within a metallic matrix powder, creating a film of yttria surrounding the larger metallic powder particles. Solid components are then produced from this mixture via SLM, during which the laser disperses the yttria particles throughout the microstructure.
Ultimately, the process eliminates the many expensive and time-consuming steps in the production of ODS alloys via traditional mechanical alloying. The process has been shown to fabricate components with 10x improvement in creep rupture life at 1100 °C and provide a 30% increase in strength over what is currently possible with 3D-printed parts.
The ODS-MEA composition may find applications where ODS alloys are currently used and in areas where such properties are desirable but the resource-intensive nature and/or inability to produce highly complex geometries via conventional processes ultimately renders their use uneconomical or infeasible. Such uses include gas turbine components (for which increasing inlet temperature enables improved efficiency) for power generation, propulsion (rockets, jet engines, etc.), industrial processes, nuclear energy applications, and sample preparation equipment in the mining and cement production industries.