Facilitating the Formation of Intermetallic Compounds in Al-Si Coatings on Steel during Hot Stamping

Abstract

Hot-stamped ultrahigh strength steel (UHSS) components are pivotal to automotive light-weighting. Steel blanks, often coated with an aluminum-silicon (Al-Si) layer to protect them from oxidation and decarburization, are austenitized within a furnace and then simultaneously quenched and formed into shape. The Al-Si coating melts within the furnace and reacts with iron from the steel to yield an intermetallic phase that provides some long-term corrosion protection. During the intermediate liquid phase, some of the coatings may transfer to the furnace components, leading to maintenance costs and operational downtime. This document describes the development of a rapid analysis method using Raman microscopy mapping to investigate the reaction mechanisms of Al-Si coating and steel during heating. A new surface modification strategy was applied on the Al-Si coating to facilitate intermetallic phase formation. This strategy provides the possibility of expediting the solidification during the heating, thus providing a method to mitigate furnace rollers’ contamination caused by melted high-temperature liquids in the industrial hot stamping process.