Sintering behaviour of Nb-16Si-25Ti-8Hf-2Cr-2Al alloy powder fabricated by a hydrogenation-dehydrogenation method

The present study investigated the sintering behaviour of Nb-16Si-25Ti-8Hf-2Cr-2Al alloy powders. The alloy powders were produced using ahydrogenation-dehydrogenation method and featured an irregular morphology. Powders sintered at 1500°C and 1600°C exhibited pores in their microstructures, while powders sintered at 1700°C for 4 h were fully densified and poreless. The cast ingot and powders were composed of three phases: Nb ss , Nb 5 Si 3 , and Nb 3 Si. However, the Nb 3 Si phase was not observed, while HfO 2 oxides formed in the sintered compact. The hafnium and oxygen reacted to form an HfO 2 oxide during the high-temperature sintering process. From the result of the thermodynamic calculation, Hf oxide formed after sintering because Hf has the highest driving force for oxidation among the elements constituting the alloy.