The role of secondary carbide precipitation on the fracture toughness of a reduced carbon white iron

The fracture toughness of a high chromium, reduced carbon white cast iron was measured using the KIc fracture toughness test. The toughness was found to increase with increasing heat treatment temperature for the temperature range of 1273-1423 K. Increases in the fracture toughness were due to crack deflection into the dendritic phase. Cracking in the dendrites was promoted by the presence of secondary carbides which formed during the high temperature heat treatment employed. The characteristic distance for brittle fracture as calculated by the Ritchie-Knott-Rice model correlated well with the centre to centre mean free path of the secondary carbides on the fracture plane.