Compressive Creep and Stress Relaxation Kinetics in a High Purity Silicon Nitride Ceramics in the 1400-1650 deg C Range

摘要

The paper presents the study of the mechanicalbehaviour at high temperature under compressive stresses of aGas Pressure Sintered silicon nitride. It is the last generation ofSi_3N_4 materials with elongated grains and a very few amountof glassy phase that explains a strong creep resistance up to1400 deg C. Stress relaxation and creep tests were achieved inthe l400-1650 deg C temperature range. The Kolhraush-Williams-Watt empirical expression is used to fit the stressrelaxation curves. The primary creep could be modelled as adelayed deformation ending by a plateau dependent ontemperature. Both creep and stress relaxation curves parameterssuggest the existence of strong microstructural changes duringtesting above 1450 deg C.