Stefan Vorberg

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.

High Temperature Strengthening Mechanisms in the Alloy Platinum- 5% Rhodium DPH

To improve the high temperature properties, platinum can be hardened by solid solution and/or oxide parti-cles. The investigated alloy, dispersion hardened plati-num-5% rhodium (Pt-5%Rh DPH), was produced via melting and subsequent annealing of the semi-fi nished product in order to obtain an oxide particle dispersion. Despite the relatively large oxide particles formed in this process, the creep strength is much higher in com-parison to conventional Pt-5%Rh. The aim of this paper is to study the strengthening mechanisms in the alloy Pt-5%Rh DPH by transmission and scanning electron microscopy. The size distribution of oxide particles shows a bimodal distribution, and the average oxide particle diameter is 315 nm for particles larger than 150 nm. For particles between 25 nm and 150 nm the average diameter is 49 nm. The size ranges of oxide par-ticles are not substantially affected by high temperature creep deformation, but particles of

Mechanical Properties of Refractory Metals at Extremely High Temperatures

Driven by the unavailibility of commercial test equipment for tensile and creep testing at temperatures up to 3000°C a measuring system has been developed and constructed at the University of Applied Sciences, Jena. These temperatures are reached with precision by heating samples directly by electric current. Contact-less strain measurements are carried out with image processing software utilizing a CCD camera system. This paper covers results of creep tests which have been conducted on TZM sheet material (thickness 2 mm) in the temperature range between 1200°C and 1600°C. It is the aim of this work to show the influence of heat-treatment conditions on creep performance in the investigated temperature range.