STRENGTH OF CRACKED CERAMICS IN HOT CORROSIVE ENVIRONMENTS

A study was conducted on the effect of surface cracks of the fracture strength of ceramics used for lower-quality fuelled gas turbines or diesel engines. Experiments were carried out on the fracture strength by bending stress and tensile stress under various test conditions. Partially stabilized zirconia, silicon carbide and silicon nitride were used for test specimens and the tests were performed in the range of 650 to 12000oC for 1.5 hours to 150 hours with and without corrosive ash. Vanadium pentoxide and/or sodium sulphate were applied on the surface of the bending test specimen and tensile test specimens were exposed to combustion gas flow containing sulphur and sodium. In order to simulate mechanical surface defects on the specimens, Vickers hardness indentation method or blast erosion damage was applied as a quantitative tool. A conventional bending machine with an electric furnace and a burner rig with a tensile loading apparatus were used in fracture strength tests. The experimental results show that the existence of artificial corrosive ash containing sodium sulphate or hold in low quality fuelled combustion gas, the fracture strength of cracked specimen is comparable to the non cracked or smooth specimen and there was no scattering among the results. On an electric furnace test the bending strength of a cracked specimen applying sodium sulphate had considerable scattering under similar test conditions. It seems this difference depends on whether the molten salt enters into the cracks or not. In the case of the burner rig tests, a dynamic pressure activate entering of gaseous or liquid molten salt into the cracks, but on the electric furnace the sodium sulphate did not always dissolve sufficiently or was not active. Some experimental facts supporting this hypothesis were obtained with EPMA. These results mean that at least on lower-quality fuelled gas turbine engines the high quality finishing work on the blade surface is useless rather than significant.

  • Supplemental Notes:
    • Ship Research Inst Japan Pprs, v 32 n 1, 1995, p 1 [26 p, 30 ref, 22 fig]
  • Authors:
    • Munkata, Y
    • Senda, T
  • Publication Date: 1995

Language

  • Japanese

Subject/Index Terms

Filing Info

  • Accession Number: 00718557
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Mar 27 1996 12:00AM