Property responses in Nb-Si-Hf-Ti-Al-W-B-Cr alloys for high-temperature applications

Multi-component Nb-(11,15)Si-5Hf-30Ti-4Al-4W-2B-(8,16)Cr alloys have been proposed, attempting to obtain the Nb-Si based alloys with a comprehensive property. The results show that three phases of NbSS, Nb₅Si ₃ and Laves Cr₂Nb exist in the alloys with a Cr content of 16 at%. With increasing Si and Cr contents the fracture toughness K_Q decreases, while the oxidation resistance at 1250°C and strength at 1250°C and 1350°C exhibit an increasing tendency. The 15Si-16Cr alloy shows the highest strength and oxidation resistance, and the lowest toughness; they are 385MPa at 1350°C, 215mg/cm² at 1250°C for 100 h, and 5.45 MPa·m^1/2 at room temperature, respectively. The 11Si-8Cr alloy with an Nb_SS/Nb₅Si₃ microstructure only has the highest toughness of 11.87 MPa·m^1/2, its strength and oxidation resistance are the lowest.