Microstructure and properties of the new Pt–Rh based alloys for high-temperature applications

Metallographic examination of the glass fibre bushings used in the process of liquid glass defibering, and of the gauzes used in the processes of catalytic ammonia oxidation, removed from operation in industrial conditions, have been made. It was found that operating life of these bushings and gauzes in the specific environmental conditions strongly depends on the mechanical properties and grain size stability of the material from which they were made. The study was carried out with an aim to determine criteria for choosing the alloys most suitable for these applications. Besides material properties, these criteria take also into account such factors as operating environment, availability of technologies and equipment for the alloys’ manufacture and processing, economic aspects and process safety requirements. Based on the results of this study, two new platinum alloys with rhodium have been developed, namely the PtRh10Y0,2 alloy for the glass industry and the PtRh10 alloy modified with boron to be used in the nitric industry. It was found that PtRh10B alloy showed smaller tendency to grain growth and had similar catalytic properties compared to those of a “classical” PtRh10 alloy. Its application in the nitric industry should enable increase of a temperature of the catalytic ammonia oxidation process and subsequently the process efficiency, and significantly reduce the emission of harmful N2O to the atmosphere, while operating life of the gauzes should be maintained at the unchanged level. Application of the PtRh10Y0,2 alloy in the production of glass fibre bushings should significantly increase their life. It is intended to carry out industrial tests aimed to assess economic benefits from using the new alloys. The possibilities of further optimisation of material choice have been discussed.