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  • Characterization of the flexural strength degradation of a commercial hot-pressed silicon nitride in a high-temperature sulphidizing environment


The results of residual strength tests on a hot-pressed silicon nitride after corrosive exposure in a simulated coal gasification environment are presented. It is shown that the weight gain of the specimens stabilises after 200 hours exposure at 1300 C and does not depend on the surface to volume ratio of the samples. For room temperature testing, an air environment can be used for reference purposes. At higher temperatures, however, the oxidation occurring in air may obscure the true effect of the corrosion exposure, and tests at high temperatures are therefore performed in nitrogen. For the as-received material, the Weibull modulus remains constant from room temperature up to 1300 C, and bulk flaws cause failure at all temperatures. In the residual strength tests at room temperature, the same value of the modulus is obtained and failure is again caused by flaws in the bulk of the material. This indicates that the exposure does not affect the intrinsic failure behaviour of the material. The corrosion induced small strength degradation can be taken into account through a reduction in the load bearing section caused by the presence of a corroded surface layer.

Additional information

Authors: SARAIVA MARTINS C, JRC Petten (NL);STEEN M, JRC Petten (NL);BRESSERS J, JRC Petten (NL);GUERRA ROSA L, Instituto Superior Técnico, Lisboa (PT)
Bibliographic Reference: Paper presented: Fracture Mechanics of Ceramics, Nagoya (JP), July 15-17, 1991
Availability: Available from (1) as Paper EN 36385 ORA
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