Influence of temperature exploitation on the failure of austenitic stainless steel

17Cr-12Ni-2.2Mo commercial unstabilised austenitic steel of AISI 316 type was additionally annealed in the temperature range from 620 to 720 degreesC for 0.5 to 20 hours after the solution annealing. Cracks perpendicularly oriented to the magistral fracture, so called splitting, were observed on fracture surfaces of selected samples after the tensile tests at room temperature. The intergranular character of these cracks was identified by fractography analysis. The presence of secondary phase particles on grain boundaries was revealed by metallographic observations. The chemical nature of Cr-rich M23C6 carbides of the particles extracted,into the carbon replicas were proved by means of TEM and EDX. Correlations between the amount of splitting and the temperature and holding time of annealing and the temperature of tensile test (-196 to 400 degreesC) was shown.