INFLUENCE OF A CRYOGENIC TREATMENT ON THE FRACTURE TOUGHNESS OF AN AISI 420 MARTENSITIC STAINLESS STEEL

Cryogenic treatments have been employed over the past three decades for both tool and high-alloy steels to improve their wear resistance, mainly through the transformation of retained austenite and the precipitation of fine carbides. However, as the enhancement of one material property is often at the expense of another, it is interesting to evaluate the effect of this type of treatments on the fracture toughness. The objective of the present work was to determine the plane-strain fracture toughness of a cryogenically treated low-carbon AISI 420 martensitic stainless steel by means of standardized fracture tests, performed in accordance with the ASTM E399 and ASTM E1820 standards. In this study, it was experimentally demonstrated that cryogenically treated specimens showed a simultaneous increase in the Km and hardness of 30 % and 5 %, respectively, compared to conventionally treated specimens.