Creep and Stress Rupture Behavior of an Advanced Silicon Nitride: Part II, Creep Rate Behavior

In Part I of this paper, experimental observations on creep testing of 74 tensile specimens of an advanced silicon nitride were presented. In this part, equations are developed for predicting creep rates in the primary and secondary regimes in the temperature range 1477–1673 K. The resulting model predicts creep strain rates to within a factor of two. The underlying phenomenological basis, which employs an activation energy approach, is discussed. The mechanisms that are likely to be responsible for the transiency of the primary creep regime and for the unique stress and temperature dependencies of the creep rates are explored.