Nb-Si intermetallic composites for high-temperature applications produced by MIM

Refractory alloys such as Nb-Si intermetallic composites exhibit low density and high strength above the operating temperature of currently applied nickel-based superalloys. Due to these advantageous properties they offer a potential to replace superalloys in structural components for high-temperature applications, such as aircraft or land-based turbines. In this study, gas atomised powder as well as high-energy mechanically alloyed powder of the recently developed alloy composition Nb-20Si-23Ti-6Al-3Cr-4Hf (at%) was produced to evaluate the feasibility for processing by MIM. A feedstock consisting of a wax-polymer based binder was successfully moulded into simple shapes. Sintering at 1500 °C for 3 hours at high vacuum showed promising results for the fine powder fraction of gas atomised powder concerning residual porosity, homogeneity of the multiphase microstructure and interstitial elements contamination. Compared to other processing technologies, the processed MIM samples reveal a very fine-grained microstructure with more homogeneously distributed silicide particles.