Qualitaetssicherung Keramischer Werkstoffe und Komponenten der Gasturbine (Quality Assurance of Ceramic Materials and Gas Turbine Components)

摘要

Nondestructive tests were performed on ceramics to assess loading capacity and acceptability. The four-point bending samples were made of reaction-bonded silicon nitride, sintered silicon nitride, and sintered silicon carbide with artificial defects (pores, impurities). The bending samples were characterized using ultrasonic and microfocus X-ray tests. The ultrasonic tests show differences between series of the same material. The series with higher sound speed tend to have higher bending strength. The defects were determined within 100 micrometers using ultrasonic microscopy and microfocus X-rays. Large Fe-parts behave differently in the three materials. Small Fe-parts (smaller than 200 micrometers) behave as a pore for all three materials. The fracture-mechanical results confirm the danger of defects close to the surface (for bending loads), requiring an intensive nondestructive surface testing.