Hybrid casting is a new fabrication concept that can reduce costs and production time of large tools, such as stamping tools for the automotive industry. In this work, we analyzed a hybrid material composed of a high chromium cast iron (HCCI) and a low carbon steel (WCB). SEM analyses indicate that the interface is free of non-metallic inclusions and porosities. The metallurgical bonding between alloys is confirmed by the diffusion of chromium and carbon from HCCI to WCB. Vickers microhardness, EDS and XRD confirmed the presence of M7C3 carbides in the HCCI and at the interface. One set of the samples was submitted to regular quenching in calm air and tempering, while another set was additionally submitted to subzero quenching before tempering. In both cases, a slight reduction of the HCCI hardness and an increase of the interface hardness were observed. The subzero treatment was effective to reduce the amount of retained austenite at the HCCI and limiting its hardness reduction. WCB microstructure and hardness showed no significative change, making it an ideal material to use with HCCI in hybrid casts. The results showed that is possible to produce bimetallic reliable components for industrial applications by means of hybrid casting.

Aerospace and automotive industries utilize advanced high strength steels due to their exceptional mechanical strength and ductility. Laser beam welding has shown potential in reducing the melted zone, heat affected zone, and process time for these steels. This study focused on dissimilar welding between DP 780 and 300M steel sheets, commonly used in the automotive and aerospace industries, respectively. The aim was to expand the range of possibilities and innovations by enabling the use of these steels in both applications. The study investigated the optimal process parameters, microstructure, and mechanical properties for the laser welding process. It also examined the influence of intercritical quenching and tempering on the microstructure and mechanical properties of the laser welded steels. The materials underwent dilution and different phase transformations due to the welding process and heat treatments, as revealed by microstructural characterization. The weld showed a notable increase in hardness, however without compromising toughness. The fractures during tensile testing occurred in the DP 780 steel, far from the MZ and HAZ. Heat treatments increased ultimate tensile strength, but lowered ductility. Welding affected the fatigue life, especially in the intercritically quenched joint, which showed a quasi-cleavage crack growth mechanism and a decrease in fracture toughness.