Creep of single crystalline and polycrystalline T2 phase in the Mo–Si–B system

The T2 phase in the Mo–Si–B system has great potential for ultra-high temperature structural applications. We examined creep of the single crystalline and polycrystalline T2 phase. The steady-state creep rate of the [021] oriented specimens is as low as 3.1×10−8 s−1 at 1500 °C and 432 MPa. The minimum creep rates at 1500 °C of the [001] oriented and polycrystalline specimens are 6.9×10−8 s−1 at 600 MPa and 3.0×10−8 s−1 at 300 MPa, respectively. The activation energy for creep was found to be ∼740 and ∼400 kJ mol−1 for [021] and [001] oriented specimens, respectively. Stress exponent for creep was found to be 6.8, 4.3 and 4.6 for [021] and [001] oriented and polycrystalline specimens, respectively. Creep resistance of the single crystalline and polycrystalline T2 specimens is much better than that of MoSi2 and Si3N4 base structural ceramics.