A FRACTOGRAPHIC STUDY OF AN OVERHEATED MEDIUM CARBON NiCrMo STEEL

Fractographic examination of an overheated-medium carbon NiCrMo steel hasbeen carried out by SEM. The rock-salt fracture occurred at the original austeniticgrain boundaries of the steel showed dimples, and the morphology and size ofMnS inclusions located in such dimples varied with different facets even for asingle austenite grain. The Widmannstatten precipitates of sulphide also occurredat the rock-salt fracture surfaces at times. The probable cause and the controllingfactors in regard to the formation of sulphide inclusions in various morphologieshave been discussed.