Effect of titanium oxide addition on magnesia refractories

This work contains the results of investigations into the influence of titanium oxide (TiO2) addition on the properties of refractory magnesia ceramics. The presented research involved adding titanium oxide in a classic way, i.e. directly to the ceramic mix. The conducted laboratory tests revealed a significant impact of this oxide on the properties of refractory materials. Addition of a small amount of TiO2 favoured the ceramic mix sintering whereas adding a bigger amount—more than 10 wt% resulted in the formation of refractories characterised by considerable porosity and low mechanical strength. Addition of this oxide also slightly improves the corrosive resistance of refractories.

CERAMIC CORES FOR TURBINE BLADES : A TOOLING PERSPECTIVE

Blade/vane components used in aerospace turbines are of twisted aerofoil shape, made by the process of investment casting, using Ni based super-alloy materials. These castings operate at turbine inlet temperatures (TET) close to the melting point of the alloy, in order to maximize thermal efficiency and thrust of the engine. The castings are made hollow, with intricate features such as turbulator, pin-fin, etc built-in to maximize the effect of heat transfer during forced cooling through internal passages. The hollow geometry in the castings is produced during the investment casting process by using a suitable ceramic core made from Silica or Alumina based mixes. These ceramic cores are high pressure injected by forcing the ceramic mix into dedicated molds or dies. Development of such dies is an involved process by itself, addressing issues right from ceramic mix behavior to manufacturability of the injection mould. The present paper attempts to highlight issues related to tooling development for ceramic cores used in investment cast turbine blade/vane components.

INFLUENCE OF SOME TECHNOLOGICAL FACTORS UPON WALL CERAMICS FROST RESISTANCE

A polynomial model, which enables evaluation of the influence of amount and graining of sand in a ceramic mix and maximum temperature and duration of burning upon ceramics frost resistance, constructed on the basis of experimental results is presented in this work. During the experiment the mass loss of ceramic specimens was measured. Experimental results were prepared for further statistical analysis with regard to linear summing of mass losses. Statistical evaluation of the quality of the constructed model and physical interpretation of tested factors were made. In addition, the authors presented the results of the samples bulking investigation in comparison with the results of frost-resistance test. Also the correlation of the results of both investigations was checked.