Markus Wenderoth

Isothermal Oxidation Behavior of a Precipitation-Hardened Pt-Base Alloy with Additions of Al, Cr and Ni

Abstract The oxidation behavior of a precipitation-hardened Pt-base alloy with 12 at.% Al, 6 at.% Cr and 5 at.% Ni was examined. At high temperatures in air this alloy forms an alumina scale and a precipitate-free layer underneath, both growing according to parabolic functions of time. Small amounts of Ni embedded in the oxide scale accelerate its growth in the initial phase of oxidation. With time, oxidation is retarded due to decreasing impurity concentration and grain coarsening in the oxide scale. The interdiffusion coefficients of the scale-forming element Al in the Pt-rich solid solution matrix are estimated.

Building a Thermodynamic Database for Platinum-Based Superalloys: Part III

Work has been ongoing in building a thermo-dynamic database for the prediction of phaseequilibria in Pt-based superalloys (1–7). The alloys arebeing developed for high-temperature applications inaggressive environments. The database will aid thedesign of alloys by enabling the calculation of thecomposition and proportions of phases present inalloys of different compositions. This paper is arevised account of work presented at the conference:Southern African Institute of Mining and Metallurgy‘Platinum Surges Ahead’ at Sun City, South Africa,from 8th to 12th October 2006 (7).Part I, describing initial results for the Pt-Al-Rusystem from the compound energy formalism model,was published in the July 2007 issue of