Development and Adaptation of UHTCMCs via Reactive Melt Infiltration of boron and zirconium diboride containing preforms
BAIER L. 1, KLOPSCH L. 1
1 German Aerospace Center , Stuttgart, Germany
Ultra-high Temperature Ceramic Matrix Composites (UHTCMCs) are a group of fibre-reinforced ceramics suitable for long term applications at temperatures above 2000°C. UHTCMCs are becoming more and more important in the aerospace sector, where materials are required for sharp edges (inlets) that are exposed to increasing temperatures due to complex flight paths, while maintaining structural stability.
The German Aerospace Center is developing this class of materials using Reactive Melt Infiltration (RMI), which creates a basis that, compared to conventional sintering processes, can provide different fibre architectures in a load-bearing manner and, thanks to fast process times, is an economical approach.
The production of the preform used for Reactive Melt Infiltration is one of the most important steps in the process, as it defines the basis for important material properties of the final ceramic, such as the matrix composition. The infiltration quality of a boron and zirconium diboride based slurry into a pitch-based carbon fabric is investigated. Different fibre and fabric types were infiltrated with a water-based slurry using a foulard. The homogeneity of the particle distribution and the infiltration properties, especially within the fibre bundle, were evaluated by CT, SEM and EDX. The preforms were then pyrolysed and infiltrated with Zr2Cu via RMI. Final SEM and EDX investigations provide information on microstructural properties such as zirconium diboride formation and distribution in the matrix and differences in the ceramics based on the different fabrics.
In addition, a slurry suitable for vacuum assisted infiltration is being researched to allow more homogeneous infiltration of boron and zirconium diboride. To this end, initial investigations into particle size and powder composition have been evaluated.
To avoid the disadvantages of the currently used zirconium-copper alloy, several new alloys have been evaluated for infiltration suitability using contact angle measurements.