Automobile manufacturers are forced to reduce the weight of the car body due to the growing restrictions on emission requirements. One way to achieve this goal is the use of high strength steels, as they can be produced by press hardening. During this process, blanks austenitized, transferred to a press and quenched during stamping to form martensite. However, the formation of oxide scale damages the stamping tools and hinders further processing, e.g. welding and painting.
In this contribution a strategy for the application of a protective coating using water-based nanoparticle dispersions is presented. For this coating, a multimodal particle size distribution is used for a low shrinkage of the green biscuit and the chemical composition is fine-tuned for an optimal temperature cycle for the hot stamping route. In contrast to previously reported coatings based on the classical sol-gel process, the protective ability of the particulate silicate coatings reaches up to 950 °C as demonstrated by thermogravimetric analysis.
The developed coating system can be compared to the Usibor® coating, which is commonly used in industry nowadays. To show the potential of the coating system, results on oxidation resistance, formability and corrosion behavior in aqueous media are shown and compared with Usibor®. Although the Usibor® coating demonstrates a better corrosion resistance in aqueous media, the temperature treatment cycle of the hot stamping route can be considerably accelerated and some disadvantages of the Usibor® coating can be avoided, e.g. the low melting point of Usibor® and the viscosity associated with it.