Effects of adding aluminum oxide or zirconium oxide fibers on ceramic molds for casting hollow turbine blades

摘要

To satisfy the requirements of mechanical performances of integral Al_2O_3-matrix ceramic mould for fabricating hollow turbine blades, Al_2O_3 or ZrO_2 fibres were added to the slurry in gelcasting. The microstructures of Al_2O_3-matrix ceramic mould were tested by scanning electron microscope and micron X-ray imaging system besides their bending strengths at different temperatures. The result showed that when Al_2O_3 fibre or ZrO_2 fibre were added, the roomtemperature bending strength of the ceramic mould was remarkably improved after pre-sintering at 1,250℃. The medium-temperature bending strength was about between 0.5 and 2 MPa from 400 to 600℃ and reached the minimum at 500℃. At 1,300℃, the high-temperature bending strengths decreased gradually with an increase of Al_2O_3 fibre content and increased with an increase of ZrO_2 fibre content. The specimens expanded first in pre-sintering and then shrunk in final sintering, respectively. According to the test results, we used ZrO_2 as the additive with 10 wt% content, and the overall performances of Al_2O_3-matrix ceramic mould were the best. Finally, hollow turbine blades were successfully fabricated.