THERMAL-SHOCK TESTING OF CERAMICS - A NEW TESTING METHOD

The thermal shock behavior of Si3N4 has been determined with a new type of computer-controlled testing equipment. Thin circular disks are heated up to 1350-degrees-C with two tungsten halogen lamps yielding heating rates up to 1000-degrees-C/s. The sample temperature is measured in situ with an infrared pyrometer and used to calculate the transient thermal stresses. The simple geometry of radially orientated notches allows in situ observation of the crack growth behavior during thermal shock. Measured failure times are used to determine the fracture toughness of the material under thermal shock loading, K(c)TS, from room temperature (RT) up to 1000-degrees-C. Comparison of the results with K(Ic)SENB values measured by the single-edge notch beam method at RT shows excellent agreement.