A Chemical/Powder Metallurgical Route to Fine-Grained Refractory Alloys
Ni-based superalloys remain state-of-the-art materials for use in the high-temperature,
corrosive environments experienced by turbine blades in gas turbine engines used for propulsion
and energy generation. Increasing the operating temperatures of turbine engines can yield
increased engine efficiencies. However, appreciably higher operational temperatures can exceed
the capabilities of Ni-based superalloys. Consequently, interest exists to develop high-melting
refractory complex concentrated alloys (RCCAs) with the potential to surpass the hightemperature property limitations of Ni-based alloys. RCCAs are multi-principal element alloys,
often comprising 5 or more elements in equal or near equal amounts. Conventional solidificationbased processing methods (e.g., arc melting) of RCCAs tend to yield coarse-grained samples with
a large degree of microsegregation, often requiring long subsequent homogenization annealing
times. Additionally, the large differences in melting temperatures of component elements can
further complicate solidification-based fabrication of RCCAs.
Herein, the feasibility of a new chemical synthesis, powder metallurgy route for generating
fine-grained, homogenous RCCAs is demonstrated. This is achieved by first employing the
Pechini method, which is a well-developed process for generating fine-grained, oxide powder
mixtures. The fine oxide powder mixture is then reduced at a low temperature (600°C-770 ºC) to
yield fine-grained metal alloy powder. Hot pressing of the metallic powder is then used to achieve
dense, fine-grained metallic alloys. While this process is demonstrated for generating fine-grained,
high-melting MoW and MoWCr alloys, this method can be readily extended to generate other finegrained RCCA compositions, including those unachievable by solidification-based processing
methods.
History
Degree Type
- Master of Science
Department
- Materials Engineering
Campus location
- West Lafayette
