What is laser hardening?
Laser hardening is a process using very high temperatures to change the microstructure of metals. A laser beam is directed at the steel’s surface and heats it close to its melting point, typically 900-1400 °C. This changes the grain to an austenitic structure.
The hot steel cools so rapidly that the steel is quenched, and a fine-grained microstructure called martensite is formed. This martensite zone can be as deep as 2 mm, improving the steel’s hardness and resistance to wear.
When is laser hardening used?
Laser hardening is used for a variety of applications, from press-forming tools to engine components and oil-drilling machinery. By locally increasing the wear resistance it extends the service life of parts. The technology is especially well suited when it is crucial to introduce as little heat into the surrounding material as possible. Cast iron and other ferrous materials, such as hardenable steels, are commonly transformed via laser hardening.
The main benefits
Laser hardening offers a number of advantages over conventional heat treatment techniques, including high throughput, reproducibility, and product quality. Localized treatment with limited heat input decreases distortion while generating a fine microstructure through rapid quench rates.
Laser hardening of Toolox® 44
Laser hardening of Toolox® 44 gives exceptionally good results due to its high yield strength. It improves the lifetime of machine components working under highly challenging conditions. The laser hardened surfaces has the further advantage of being very smooth. This reduces friction and the risk for material sticking to the surface. To further enhance the hardness of the surface, carbon powder can be used to cover the metal surface during the process. In this way, Toolox® can reach a surface hardness as high as 800 HV. For Toolox® 33, 700 HV can be obtained.
Other types of surface treatment
Gas nitriding
A common technique for giving steel a hard surface is gas nitriding.
It functions by introducing nitrogen from a nitrogen-rich gas into the steel.
This process is also known as ammonia nitriding since the gas is usually ammonia (NH3).
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. The hot steel part is quenching in water, oil, or a polymer-based liquid.
Surface etching
Chemical or photo etching are two terms used to describe the surface etching of metal. It is a type of subtractive metal machining that modifies the surface geometry of a steel item using chemistry, such as when constructing steel molds for automobile interior panels.
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 reduces the risk for propagation of microcracks in the surface.
An excellent tool steel for surface treatment
A homogeneous steel with high surface quality and uniform characteristics is ideal for all kinds of surface treatments. Toolox® engineering and tool steel from SSAB fulfil your strictest demands for laser hardening and other surface treatment techniques.