|About this Abstract
||2016 TMS Annual Meeting & Exhibition
||Phase Transformations in Multi-component Systems: An MPMD Symposium Honoring Gary R. Purdy
||Pt-Rh Failure through Distinct Phosphorus Diffusion Mechanisms
||Anna Nakano, James Bennett, Jinichiro Nakano
|On-Site Speaker (Planned)
Certain gaseous species; including arsenic, phosphorous, and sulfur; would cause Pt-Rh thermocouples to fail if used in reducing atmospheres at elevated temperatures. Unlike sulfur and arsenic, sensor degradation by phosphorous has not been well known. In this work, Pt-Rhx alloys were interacted with gaseous phosphorous oxide to study the failure mechanism in various oxygen partial pressures. The analysis revealed material degradation was caused by a combination of 1) Pt liquidus lowering and 2) intermediate phase formation at grain boundaries or gas/solid interfaces through two distinct phosphorous diffusion routes dependent on Rh alloying content: intergranular for low Rh alloys and intragranular for high Rh content. A critical chemical border between intergranular and intragranular was also investigated using a diffusion couple technique between pure Pt and Pt-30wt.% Rh. The general failure mechanisms of the Pt-Rh thermocouples by phosphorous under conditions studied will be discussed.
||Planned: A print-only volume