Abstract
The effects of hardness and prior austenite grain size on the impact property of hot work tool steel JIS-SKD6 at room temperature were investigated by the analyses of impact fracture surface and of load-deflection diagrams obtained from instrumented Charpy impact test. In order to vary hardness and the grain size, the specimens of SKD6 produced by ingot and powder metallurgy were quenched from different temperatures, i.e., 1303K and 1403K, and then tempered twice at 873K. It was found that most of impact energy was exhausted in crack initiation for every material and the impact fracture modes were divided into three groups. Although the impact energy tended to decrease with increasing hardness, fine-grained structure suppressed the reduction in impact energy due to the enhancement of the resistance to the crack initiation.
