CERAMIC COMPONENT PROCESSING DEVELOPMENT FOR ADVANCED GAS-TURBINE ENGINES

Norton/TRW Ceramics (NTC) is developing ceramic components as part of the DOE-sponsored Advanced Turbine Technology Applications Project (ATTAP). NTC's work is directed at developing manufacturing technologies for rotors, stators, vane-seat platforms, and scrolls. The first three components are being produced from a HIPed Si3N4, designated NT154, Scrolls were prepared from a series of siliconized silicon-carbide (Si-SiC) materials designated NT235 and NT230. Efforts during the first three years of this five-year program are reported. Developmental work has been conducted on all aspects of the fabrication process using Taguchi experimental design techniques. Appropriate materials and processing conditions were selected for power beneficiation, densification, and heat-treatment operations. Component forming has been conducted using thermal-plastic-based injection molding (IM), pressure slip-casting (PSC), and Quick-Set(TM) injection molding.1 An assessment of material properties for various components from each material and process were made. For NT154, characteristic room-temperature strengths and Weibull Moduli were found to range between almost-equal-to 920 MPa to almost-equal-to 1 GPa and almost-equal-to 10 to almost-equal-to 19, respectively. Process-induced inclusions proved to be the dominant strength-limiting defect regardless of the chosen forming method. Correction of the lower observed values is being addressed through equipment changes and upgrades. For the NT230 and NT235 Si-SiC, characteristic room-temperature strengths and Weibull Moduli ranged from almost-equal-to 240 to almost-equal-to 420 MPa, and 8 to 10, respectively. At 1370-degrees-C, strength values for both the HIPed Si3N4 and the Si-SiC materials ranged from almost-equal-to 480 MPa to almost-equal-to 690 MPa. The durability of these materials as engine components is currently being evaluated.