Sub-Zero Treatment of Cold Work Tool Steels – Metallurgical Background and the Effect on Microstructure and Properties*

Abstract

Abstract Sub-zero treatment is a commonly accepted process that is intended to increase the hardness, wear resistance and dimensional stability of tool steels and components over several decades. However, the metallurgical background of the phenomena responsible for these improvements is not yet entirely clear. Several theories have attempted to clarify the phenomena taking place during sub-zero treatment and their effect on the microstructure and properties of steels, but all of them manifested significant drawbacks from the point of view of generally accepted metallurgical theories. In this study, these theories are discussed based upon the results obtained by comprehensive investigations of sub-zero treatment of powder metallurgy-made Cr-V Vanadis 6 ledeburitic tool steel. A new theory respecting the main physical-metallurgical principles is also established.