A group out of Missouri University of Science and Technology says it has a new method for mixing metals with ceramic that will allow stronger, heat-resistant, functionally graded materials for the creation of hypersonic and other ultrahigh-temperature aerospace components.
The group, led by Ming Lue, a mechanical and aerospace engineering professor at S&T, uses a precisely controlled extrusion approach to combine – in varying proportions – the ceramic and metallic base components together with a binder. For example, zirconium carbide is pushed through one tube, tungsten is pushed through a second tube and the binder from a third. The metal–ceramic combination is then extruded as a paste, but interesting thing is that the exact mix could be carefully altered as a function of time.
This could potentially revolutionize manufacturing of complex- near net-shaped ceramic parts (which can’t be processed by conventional methods such as slip casting or injection molding).
In other words, a manufacturer could produce a component with a paste composition that can be varied as it is extruded.
The piece is made depositing the paste, layer-by-layer. The component is then put through what they call Rapid Freeze Prototyping and Freeze Casting to remove the water and polymer binder. The last step is a reaction sintering. The end result is a component composed of gradient materials with custom-tailored mechanical properties.
The biggest benefit, says Leu, who is associated with S&T’s Center for Aerospace Manufacturing Technologies, is the ease it would give manufacturers to create customized parts for aircraft or spacecraft. “By controlling the extrusion forces, we can customize the percentage composition of each of the materials in the final product,” says Leu, who worked on the project with Greg Hilmas, a professor of materials science and engineering and Robert Landers, an associate professor of mechanical and aerospace engineering.
Another benefit is that the process cuts the amount of polymer needed to bind the metal and ceramic.
“In order to create high-performance combustion components or high-performance hypersonic vehicles that can sustain extreme heat and minimize thermal stresses, these types of functionally graded materials will be needed,” says Leu.