Development of a cohesive joining method for glassy carbon and a C / C-SiCN composite material for an innovative high-temperature measuring system

Conventional high temperature (>1400 degree C) measuring techniques are very limited. Thermal protective covering of temperature measuring elements in molten metals usually are single-use systems. As a part of a research and development project a new temperature measuring system is being developed. The requirements for this protective cover are extremely complex. Not only does it has to be resistant to high temperatures, media in molten metals, fractures and thermal shocks, it also has to be gastight and thermal conductive. The compounds used currently for these covers don't fit this profile. Laminated C/(C/C-SiCN) hybrid composites are a new approach, consisting of glassy carbon and a C/C-SiCN composite. In order to ensure the media resistance of the protective cover a fitting lamination is applied by means of a thermal spraying. Due to the extreme requirements of the joining points the joining of this lens barrel hybrid composite with the gastight seal is quite difficult. The joints have to maintain an adequate mechanical stability and gasthightness for up to 700 degree C. Other reliable joining techniques for graphite are supposed to be applied to glassy carbon. Regarding this active hard soldering was investigated. In this article conventional active hard soldering agents with varying titanium contents and under variation of other parameters are tested for their suitability as a soldering agent. The soldered samples were material graphically, micromechanically and fractographically characterised.Original Abstract: Konventionelle Temperaturmessungen im Hochtemperaturbereich (>1400 degree C) unterliegen starken Einschraenkungen. Thermoelementschutzhuellen fuer Temperaturmessungen in Metallschmelzen sind mehrheitlich Einwegsysteme. Im Rahmen eines FuE-Projektes wird ein neuartiges Temperaturmesssystem entwickelt. Die Anforderungen an die Schutzhuelle sind komplex. Sie muss sowohl temperaturbestaendig, medienbestaendig in Metallschmelzen, gasdicht, thermoschockbestaendig, waermeleitfaehig als auch bruchzaeh sein. Die zurzeit eingesetzten Werkstoffe fuer die Schutzsysteme erfuellen diese Anforderungen nicht. Einen neuen Ansatz stellt ein beschichteter C/(C/C-SiCN)-Hybridverbund dar, welcher aus Glaskohlenstoff sowie aus einem C/C-SiCN-Verbund besteht. Um die Medienbestaendigkeit der Schutzhuelle zu gewaehrleisten, wird je nach Anwendungsfall eine entsprechende Beschichtung durch ein thermisches Spritzverfahren appliziert. Das Fuegen des Tubus-Hybridverbunde