Papers by Author: David F. Lupton

Abstract: The broad application of platinum and platinum alloys results from their excellent high temperature mechanical properties as well as their near-perfect oxidation resistance and their outstanding resistance to corrosive attack by metal oxide melts such as fluxing agents. However, a few basic rules must be adhered to if platinum devices are to give satisfactory service. Platinum is susceptible to “platinum poisons” and other impurities. These “poisons”, the reasons for their corrosive effects, and techniques for minimizing or eliminating their influence are outlined.

Abstract: For the production of endless glass fibres, the use of glass fibre bushings made of PtRh alloys is necessary. The manufacturing process for high melting glass fibres in particular leads to simultaneous chemical attack and mechanical loading at extremely high temperatures.The influence of these complex loadings on the stress-rupture strength and the creep behaviour of various PtRh alloys (conventional and oxide dispersion strengthened alloys) was investigated after contact with various glass melts. The investigations include both long-term tests under service conditions and laboratory corrosion tests. The investigations will be complemented with metallographic and fracture examinations in the SEM and microprobe analysis.Furthermore, the fibre manufacturing process is influenced by the wetting of the bushing material by the glass melt. For this reason the wetting behaviour of the platinum materials in contact with the different glass melts was investigated as a function of the working temperature of the glass fibre bushings. The results of the investigations provide a basis to optimise materials selection for glass fibre bushings.

Abstract: Due to its outstanding mechanical properties at high temperatures and chemical stability iridium is used for demanding high temperature applications. In order to obtain materials data necessary for the design of high temperature equipment and the numerical simulation of their service performance the stress-rupture strength and creep behaviour have been investigated in a temperature range between 1650°C and 2300°C. The results of metallographic and fracture examinations (SEM) revealed that, in common with other pure metals, unalloyed iridium shows marked grain growth at high temperatures. Under these conditions, the deformation characteristics of iridium may not be entirely uniform and predictable, as will be demonstrated with examples from the creep studies. Both metallographic examination and investigations by means of scanning electron microscopy gave indications of possible causes for a significant anomaly in the creep behaviour. It is therefore advantageous for the mechanical properties if a fine-grained microstructure can be maintained even at the highest service temperatures.