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In the present work, the wetting behaviour of the Cu–GaX (X = 10–30 wt.%) liquid alloys on 304L steel was investigated in vacuum at temperatures between 1123 and 1373 K. Contact angle and surface tension measurements were performed using the sessile drop setup. In general, the Cu–GaX (X = 10–30 wt.%) alloys show good or even excellent wetting on 304L steel. However, the wetting mechanism strongly depends on the Ga content. While for Ga-poor alloys secondary wetting occurs, there is a partial dissolution of steel grains combined with an austenite-to-ferrite transformation for larger Ga contents. Cu penetrates along the grain boundaries of the substrate and provides a path for Ga diffusion into the steel. The dissolution of steel grains at the interface is suggested to be responsible for slowing down of the spreading at elevated temperatures. Understanding these interrelations between microscopic and macroscopic effects is important for the development of new Cu-based liquid alloys containing Ga, especially for applications involving steels. Keywords: Brazing, Reactive wetting, Gallium, Copper, Steel, Phase transformation

This paper demonstrates the successful processing of a high-strength Fe85Cr4Mo8V2C1 tool steel by selective laser melting (SLM). Based on tailored parameter variation studies, crack-free and highly dense FeCrMoVC parts (99.99% relative density) are obtained by this processing method. The applied localized high heat inputs during very short interaction times result in a fine, homogeneous microstructure composed of martensite, austenite, and carbides. This combination of phases together with the morphology of the microstructure results in excellent mechanical properties, such as a microhardness of 900 HV 0.1 (ca. 67 HRC) and a compressive strength of about 3800 MPa combined with a fracture strain up to 15%. Therefore, the SLM processing of this alloy enables a further increase of the hardness and compressive strength compared to the as-cast state.Altogether, processing the FeCrMoVC steel by SLM as one key additive manufacturing technology shows high potential for advanced tool design. Keywords: Selective laser melting, Steel, Microstructure, Hardness, Mechanical properties