Alumina-Mullite Refractories: Prototypal Components Production for Thermal Shock Tests

Alumina-mullite refractory tiles are used as liners in gas turbines for power production, for the thermal insulation of the combustion chambers. The typical microstructure is characterized by a coarse fraction, in order to increase porosity (and hence thermal insulation) and improve thermal shock resistance (by grain bridging mechanism). A mixture of alumina and ceramic wastes was optimized to manufacture prototypal components, by cold isostatic press (CIP). On sintering at 1600°C, a final composition of 40% mullite and 60% alumina was obtained. For the production of refractory tiles with dimensions similar to the commercial ones, an appropriate mould was CAD-CAM designed and produced, using aluminium and silicone. 115 x 95 x 30 mm3 tiles were obtained and utilized for thermal shock tests. Samples were heated up to 1000°C and quenched to 20°C: this cycle was repeated 30 times before inspecting the macroscopic cracks. The results were compared with those obtained with a standard test for advanced technical ceramics based on MOR measurements. Two different pressing conditions were tested (60 and 150 MPa) in order to get data about a possible industrial production by uniaxial pressing.