An implementation of new ultra-high temperature materials that would be able to operate beyond superalloys regime requires using novel materials technology design approaches. In this regard, a special attention is given to the concept of multicomponent alloys produced by mixing refractory metals (such as Mo, Nb, Ta and W) in near equal fractions. Such kind of materials having melting points above 2000°C are referred to as Refractory High Entropy Alloys (RHEA) or Refractory Complex Concentrated Alloys (RCCA), depending on a chemistry/structure complexity, and in many cases they exhibit mechanical properties at very high level (completely unattainable for the superalloys) even at temperatures as high as 1600°C. However, the main drawbacks hindering a successful substitution of superalloys by new RHEAs are mostly related with: (I) a rather poor oxidation resistance on refractory metals at intermediate temperatures (below 900°C) and (II) a much higher density (~13-14 vs. 8-9 g/cm3) as compared to nickel based alloys.

In the CoSMIc Project we propose to overcome the aforementioned limitations by introducing a novel class of lightweight ultra-high temperature materials that combine the concept of RCCA with high strength oxidation resistant intermetallics containing silicon (silicides), boron (borides) and/or silicon-boron (borosilicides). Accordingly, we propose to call them boron enhanced complex concentrated silicides (BECCS). We expect that these new materials will exhibit the following advantages over nickel superalloys and “conventional” refractory alloys: (i) a relatively low density (6-7 g/cm³); (ii) an improved oxidation resistance (up to 1600°C) due to formation of continuous borosilica glass surface layer; (iii) a superior structural thermal stability ensured by a high configurational entropy of involved phases and (iv) an enhanced high temperature strength due to in-situ reinforcement by superhard high entropy borides and borosilicides.

Additionally, our engineering goal is to develop a new fabrication method of the BECCSs that would allow their processing under temperature/pressure conditions lower than that proposed in the literature for similar materials, as well as without using any toxic chemical substances as activators.