The strain–time relationship was recorded, and the creep exponents and activation energies of the creep have been calculated. The creep micromechanisms have been also studied by means of scanning electron microscopy.
The obtained creep stress exponent varied from 0.05 to 1.12 and the obtained activation energy in the interval from 215 to 329 kJ/mol. The main creep mechanisms are densification of the sub-layers with fine columnar crystals, bending of crystals and leaning down of sets of crystals.