Material development of oxide based CMCs and Manufacturing of complex turbine parts (prototypes shroud and combuster)
Oxide based CMCs were developed by novel manufacture routes with main works on matrix development and fibre coatings. As ceramic fibre a commercial NextelTM 720 fibre was used. Different batches of materials were developed and characterised in terms of mechanical strength, density and high temperature behaviour. Manufacture techniques were developed for complex turbine prototypes like a shroud and a combuster. The tests show a high potential for this type of material up to 1050°C even for long term use. Above this temperature the material suffers from degradation effects of the ceramic fibre. However the material still can be used for short term high temperature applications like rocket nozzles or thermal protection systems.
The targets of this activity was extension of the processing capabilities of a laboratory scale fibre coating reactor to produce in continuous mode reproducible coatings on each of the individual filaments of Nextel 720 multifilament fibre tows over lengths of the order of thousands of meters setting-up of a specific low temperature Metal Organic Chemical Vapor Deposition (MOCVD) process to deposit Zirconia coatings onto Nextel 720 fibre tows and subsequent optimisation of this novel coating system for the manufacture of the combustor and shroud. The final goal was the development of a novel ZrO2/Nextel 720 coating/fibre system, which involved three different phases with the following objectives: -development of CVD process for a new coating composition -Setting-up of a continuous mode deposition process -Fabrication of CVD coated fibres.
A complete set of NDE methodologies (consisting of Ultrasonic and Acoustic Emission) applied for the non-destructive characterization of all the Oxide/Oxide Ceramic Composites and Components which developed within the frame of the CERCO project. Classical ultrasonic inspection was used for the examination of the integrity, quality and homogeneity of the produced materials and full components. An innovative ultrasonic based methodology was also used for the stiffness matrix measurement of the Oxide/Oxide materials and based on this the degradation of the stiffness matrix components as a function of the working time of the material under simulated gas turbine conditions was provided. Finally the anisotropic damage functions of all the Oxide/Oxide materials developed within the frame of CERCO project versus the exposure period at simulated gas turbine working environment was calculated. Continuous Acoustic Emission (AE) monitoring and Pattern Recognition analysis of AE signals applied to all the quasi-static tests at room temperature both on as the received and the exposed at simulated gas turbine working conditions test samples. Based on these results a complete characterization of the damage modes and the failure mechanisms of the Oxide/Oxide materials were provided.