Study On Removing Of Alumina Ceramic Cores For Nickel Base Single Crystal Turbine Blades

The main way to improve the overall performance of aero-engine blades is improvingthe cooling efficiency. The key technology is the manufacturing of efficient air-cooledblades and ceramic core removal after casting blade. Alumina-based ceramic core hasexcellent metallurgy chemical stability and creep resistance, which can ensure complexcavity structure orientation and dimensions of the column precision and yield hollow singlecrystal blades reducing the manufacturing cost. As a result, alumina-based ceramic corebecomes the first choice of a senior single crystal and eutectic casting core material. Butthe low removal rate and removal efficiency of alumina-based ceramic core cannot meetthe needs of industrial production. Thus, the rapid removal technology of alumina-basedceramic core becomes the key issues to be solved leading the alumina-based ceramic coreto be used widely.In this paper, the dissolution kinetics of fused corundum in potassium hydroxidesolution and sodium hydroxide solution was studied. The influences of the dissolutiontemperature, alkali concentration and reaction time on the dissolution kinetics of fusedcorundum were revealed. A dissolution kinetics model was established, and the simulatedresults indicate that the main controlled step of reactions is chemical reaction in bothalkaline solution. The temperature and pressure curves in the autoclave was obtained underdifferent conditions of alkali concentration, and the variation relationship of pressure andtemperature in the reaction system were determined under different alkali concentration,volume filling factor and pre-filled nitrogen conditions. The effects of reaction temperature,reaction pressure and reaction time on the rate of removal core systems, the optimumconditions for the removal of the core is that liquid hydrogen hydroxide concentration70%,temperature385℃, pressure22MPa. The nickel-base single crystal can be completelyremoved from turbine blades of alumina based ceramic core within30hours and nosignificant corrosion on the leaf surface.