Boron-doped molybdenum silicides for structural applications

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 1999-03, Vol.261 (1), p.16-23
• Main Authors: Akinc, Mufit, Meyer, Mitchell K., Kramer, Matthew J., Thom, Andrew J., Huebsch, Jesse J., Cook, Bruce
• Format: Article
• Language: English
• Subjects: Corrosion protection; Creep strength; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Molybdenum silicides; Oxidation protection; Physics; Surface treatments
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(98)01045-4

The addition of as little as 1 wt.% (=3 at.%) boron improved the oxidation resistance of Mo 5Si 3 by as much as five orders of magnitude over a temperature range of 800–1500°C. The mechanism of oxidation protection is the formation of a borosilicate glass scale that flows to form a passivating layer over the base intermetallic. The compositional homogeneity range for T1 (Mo 5Si 3B x) phase was determined to be much smaller than that reported previously by Nowotny. Compressive creep measurements show that materials based on the phase assemblage of T1-T2 (Mo 5SiB 2)–Mo 3Si have high creep strengths similar to single phase Mo 5Si 3. Electrical resistivity of selected compositions was also measured and varied from ≈0.06 mΩ-cm at room temperature to 0.14 mΩ-cm at 1500°C. Temperature coefficient of resistivity (TCR) was estimated to be on the order of 1×10 −4 C −1 for most compositions.