Investigating the change in wear behaviour of a tool steel after surface melting and gaseous alloying

In this study it is shown that surface melting in the presence of a reactive gas can be used as a method of changing the tribological properties of a hot forging die steel. A H13 tool steel surface was melted in the presence of a gaseous shield of pure argon, nitrogen, carbon dioxide and a mixture of 80% carbon dioxide–20% argon. Microhardness profile measurements and metallographic examination was used to study the changes in wear behaviour after surface modification. The results indicate a significant increase in surface hardness after the melting and gaseous alloying process with the most wear resistant surfaces produced under a shield of CO₂ and CO₂–Ar gases. This was attributed to the formation of a fine dendritic microstructure consisting of chromium–vanadium carbides. The presence of these hard phases in the surface reduce the degree of plastic deformation and wear by adhesive mechanisms.