The creep behaviour of Synroc and alumina

The creep of Synroc C and alumina in four-point bending in argon was investigated in terms of the relaxed symmetric stress and the reference asymmetric stress; the alumina being used as a reference material. The creep tests were undertaken in the temperature range from 850°C to 1300°C. The rupture behaviour of Synroc at 950°C indicated a high stress exponent, and that the creep ductility was unusual in that the strain increased with increasing test time. A scanning electron miscroscopy examination of Synroc after creep revealed the development of defect-free oxidised surface layers. For Synroc, neither prior exposure to pre-heating in air, nor prior indentation affected the creep rate behaviour. This was attributed to the formation of the oxidised surface layers and the associated healing effects of the damage produced by the indentations.