Subcritical crack growth in SiAlON ceramics from a modified static lifetime test including multiple use of survivals

A new method was investigated to show subcritical crack growth in SiAlON ceramics from a modified static lifetime test including multiple use of survivals. SiAlON ceramics can be derived from both Α- and β-silicon nitride modifications by substituting silicon by aluminum and nitrogen by oxygen. Nd2O3 was used as sintering additive in the starting powder mixtures for the fabrication of a mixed Α/β-SiAlON. The slurry was subsequently dried in a rotatory evaporator, and finally sieved. Sintering was performed in nitrogen atmosphere in a BN-crucible using a hotisostatic press with a graphite resistance heater. The powder compacts were heated at a rate of 10 K/min to the maximum sintering temperature of 1,830°C. Subcritical crack growth is governed by the stress intensity factor K, and for a given material, there is a unique relation between the crack growth rate. SiAlON ceramic investigated under distilled water indicates hardly any environmental-assisted subcritical crack growth.