Surface treatment of tool steel

What is steel surface treatment?

Surface treatment will improve the service life and performance of a wide range of steel applications. This is achieved by many different techniques involving gas, laser, mechanical tools, or chemicals. The goal is to increase the hardness or the fatigue resistance of the steel’s surface – in many cases both. Chemical treatment is usually applied to alter the structure of the surface, without changing the mechanical properties of the steel.

What is surface treatment used for?

Gears, screws, crankshafts, cams, molds, dies and stamping tools are some examples of applications that benefit from surface treatment. A harder surface will resist wear, making it last longer. Improved fatigue resistance will make a steel component stand up to many more loading cycles.

Different types of steel surface treatment

Surface etching

Chemical or photo etching are two terms used to describe the surface etching of metal. It is a kind of subtractive metal machining that changes the surface structure of a steel part using chemistry. One example of surface etching is when making steel molds for automobile interior panels.

Gas nitriding

Gas nitrided steel gets a harder surface and also usually becomes more resistant to corrosion. Gas nitriding is performed at a relatively low temperature, typically 520 °C. It works by diffusing nitrogen into the steel from a nitrogen-rich gas. The gas is usually ammonia (NH3). 

Laser hardening

Laser hardening uses a laser beam to heat up the steel’s surface close to its melting point, typically 900-1400 °C. This changes the grain to an austenitic structure. Rapid cooling transforms the grain to a martensitic structure. The martensite zone can be as deep as 2 mm, improving the steel’s hardness and resistance to wear.

Shot peening

In shot peening, spherical metallic, glass, or ceramic particles are struck against the steel surface with enough energy to cause plastic deformation. This compresses the steel's surface, which improves the fatigue resistance and reduces the risk for propagation of microcracks in the surface. 

Laser peening

Laser peening works by a laser pulse that creates a pressure wave which penetrates deep into the metal. This causes compressive residual stresses in the steel, counteracting tensile stresses that lead to corrosion, fatigue and cracking. 

Induction hardening

By using an alternating magnetic field, induction hardening heats the steel to a high temperature after which it is immediately quenched. The surface layer is changed to form a martensitic structure, which is harder than the base metal. 

Toolox® is the right choice for steel surface treatment

Toolox® is a prehardened and exceptionally clean tool steel with great properties for all kinds of surface treatments, whether it’s to increase wear or fatigue resistance or a combination. A versatile tool steel such as Toolox® lends itself perfectly to high-performing machine components, molds, dies and stamping tools.