Bonding Strength of Hot-Formed Steel with an AlSi Coating and Approaches to Improve It by Laser Surface Engineering

Hot-formed high strength steels like 22MnB5+AS150 with an aluminum-silicon (AlSi) coating are widely used in modern cars for lightweight and safety purpose. An advantage of the AlSi-coating is its property to be suitable for direct hot forming, because it protects the steel from oxidation and decarburization during the process. Brittle phases in the coating arise due to temperature driven diffusion during the hot forming process. These phases are responsible for a reduced bonding strength of about 30% at dynamic loading. If the brittle coating is removed e.g. by a shot blasting process, the bonding strength can be improved to a maximum, only restricted by the geometry and adhesive properties. The same effect can be observed if the coating is remelted by a laser instead of removing.