Compressive creep of fine and coarse-grained T 3SiC 2 in air in the 1100–1300 °C temperature range

Abstract

Herein, we report on the compressive creep behavior of hot isostatically pressed (HIPed) fine-grained (FG) and coarse-grained (CG) Ti 3SiC 2 in the 1100–1300 °C temperature range. The creep behavior is characterized by three regimes, a primary, quasi-steady state and a tertiary. At lower stresses, the creep rates of the two microstructures are comparable suggesting that dislocation creep is operative. At ≈2, the stress exponents in the quasi-steady state regime are comparable to those measured in tension; the creep rates in compression, however, are roughly an order of magnitude lower. At relatively high stresses and/or temperatures, the stress exponents of the FG samples increase dramatically and the creep rates of the CG samples are higher than their FG counterparts. Both observations suggest a change of mechanism from dislocation creep to possibly sub-critical crack growth, in which delaminations play an important role. This conclusion is bolstered by post-deformation microstructural analysis that shows evidence for sub-critical crack growth. The minimum creep rates of pressureless sintered Ti 3SiC 2 samples were roughly an order of magnitude higher than HIPed samples, with comparable grain size strongly suggesting that some form of grain boundary related deformation, such as decohesion and/or sliding, is playing an important role in the sintered samples.