MSE PhD Defense - William Daloz

Wednesday, September 16, 3 p.m.

MRDC 3515 (Hightower Conference Room)

Thesis Committee:

Prof. Joe Cochran (advisor), MSE

Prof. David McDowell, ME/MSE

Prof. Rick Neu, ME

Prof. Thomas Sanders, MSE

Prof. Naresh Thadhani, MSE

Title: Developing a High Temperature Oxidation Resistant Mo-Si02 Composite Alloy

Abstract:

A new powder processing approach to produce oxidation resistant molybdenum alloys for high temperature use has been developed. Oxidation protection is provided by fine dispersion of silica glass particles within a molybdenum matrix. As the molybdenum oxidizes, the glass is exposed and melts to form a self-healing protective oxide coating. Additionally, homogeneously dispersed Mo5SiB2 and/or Mo2B provide boria upon oxidation which reduces glass viscosity and allows flowing glass to coat the surface while remaining solid internally. This is similar to the oxidation protection used in Mo-3Si-1B (wt%) systems; however embedding the glass directly into the Mo matrix and eliminating the Mo3Si (A15) phase provides the same volume of glass at lower volume fractions of brittle phases and also without embrittling Si impurities in solution in Mo. Additionally the glass composition can be tailored for different applications and different temperatures beyond that achievable in Mo-Si-B based systems. A variety of microstructures, compositions and additional components for improved oxidation protection are also explored, and mechanisms of the oxidation protection are discussed.