Microfractography in failure analysis of cold forging dies

In this paper microfractographic features in fracture surfaces for tensile, fatigue, impact and three point bending of cold forging die steels with Rockwell C scale hardness number of 52–68 is presented. The emphasis is placed upon the stretched zone formation ahead of fatigue crack and the relation between the stretched zone width and fracture toughness of these cold forging die steels. Finally it is briefly described that the quantitative analysis for cold forging die failure can be possible by measuring the stretched zone width.