Abstract
Thermal shock tests were carried out on AISI 304 steel and tool steel (JIS SKD62) by using a new thermal shock testing apparatus. Analysis of their quasi-static thermal stress intensity factors was performed. Fractographic features of thermal shock cracking were examined. Then, the critical J-integral values corresponding to the critical stretched zone widths were evaluated by applying the JIc test concept. These values were compared with the fracture toughness values obtained in the same high temperature range.
The results obtained are summarized as follows;
(1) Fracture toughness under thermal shock can be evaluated by means of either the analysis of quasi-static thermal stress intensity factor or the application of JIc test concept.
(2) The fracture toughness values under thermal shock are smaller than the fracture toughness values with in the same high temperature range.
(3) An intergranular facet pattern is observed for thermal shock cracking, whereas a dimple pattern is mainly observed on a fracture toughness specimen. The difference of fracture mode corresponds to the degree of disagreement between the fracture toughness under thermal shock and the fracture toughness at a high temperature.
