Property Responses in Nb-Si-Hf-Ti-Al-W-B-Cr Alloys for High-Temperature Applications

Abstract

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, Nb5Si3 and Laves Cr2Nb exist in the alloys with a Cr content of 16 at%. With increasing Si and Cr contents the fracture toughness KQ 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•m1/2 at room temperature, respectively. The 11Si-8Cr alloy with an NbSS/Nb5Si3 microstructure only has the highest toughness of 11.87 MPa•m1/2, its strength and oxidation resistance are the lowest.

Oxidation and Microstructural Behaviors of Ni-Based Alloys Strengthened by (Ta, Hf)C Carbides at 1250 °C in Air

“…-25Cr-0.4C-6M with M = 2/3 Ta and 1/3 Hf for one alloy (named "T alloy") or M = 2/3 Hf and 1/3 Ta for the second alloy (named "H alloy"). This supposes the introduction of hafnium with unusually high concentrations (2 and 4 wt.% Hf), compared to other Ni-based superalloys [12,13], nickel aluminides [14], single crystals [15], Nb-based refractory alloys [16,17] or HEAs (High Entropy Alloys) [18][19][20].…”

Oxidation and Microstructural Behaviors at 1200 °C of 32.5 wt.% Cr–Containing Co–Based Alloys Strengthened by HfC Carbides

“…Hafnium has been known for several decades as an important element for superalloys [4], even if it is not frequently met in their chemical compositions. Its recognized beneficial effects are related to the resistance against oxidation at high temperature of alloys of various families: NiAl or NiAlPt alloys [5,6], NbAlV alloys [7], NbSiCr alloys [8] and high entropy alloys [9][10][11]. However, hafnium is also a strong MC-forming element (MC: monocarbide), leading notably to carbides which show remarkable stability at elevated temperatures in cobalt-based model alloys [12].…”