Surface hardening of tool steel

Surface hardening is used to – as the name implies – create a surface that is harder than the original steel. The harder surface makes for higher performing machine components, molds, dies and stamping tools. Knives and blades in for example recycling equipment will stay sharp for longer. Molds and dies that work with abrasive materials will get a longer productive life. Other common applications are crankshafts, camshafts, valve parts, gears, and screws.

There are different methods to achieve the desired hardness of the steel’s surface. One method relies on heating the steel close to its melting point, typically 900-1400 °C. This changes the grain to an austenitic structure. When the heat is removed the steel cools so rapidly that it is quenched, and a fine-grained microstructure called martensite is formed. The martensite zone can be as deep as 2 mm, improving the steel’s hardness and resistance to wear. 

There is also a low-temperature method for surface hardening, gas nitriding which will be discussed below.

Toolox^® is a clean tool steel with high surface quality and properties that make it highly suitable for surface hardening and other types of surface treatment techniques. It’s a prehardened steel used for machine components, molds, dies and stamping tools.