Two magnetron sputter targets of CoCrFeNi High-Entropy Alloy (HEA), both in equal atomic ratio, were prepared by spark plasma sintering. One of the targets was fabricated from a homogeneous HEA powder produced via gas atomisation; for the second target, a mixture of pure element powders was used. Economic benefits can be achieved by mixing pure powders in the intended ratio in comparison to the gas atomisation of the specific alloy composition. In this work, thin films deposited via magnetron sputtering from both targets are analysed. The surface elemental composition is investigated by X-ray photoelectron spectroscopy, whereas the bulk stoichiometry is measured by X-ray fluorescence spectroscopy. Phase information and surface microstructure are investigated using X-ray diffraction and scanning electron microscopy, respectively. It is demonstrated that the stoichiometry, phase composition and microscopic structure of the as-deposited HEA thin films are almost identical if the same deposition parameters are used.

Molybdenum–nickel materials are catalysts of industrial interest for the hydrogen evolution reaction (HER). Well-characterized surfaces of the single-phase intermetallic compounds Ni7Mo7, Ni3Mo, and Ni4Mo were subjected to accelerated durability tests (ADTs) and thorough characterization to unravel whether crystallographic ordering affects the activity. Their intrinsic instability leads to molybdenum leaching, resulting in higher specific surface areas and nickel-enriched surfaces. These are more prone to form Ni­(OH)2 layers, which leads to deactivation of the Mo–Ni materials. The crystal structure of the intermetallic compounds has, due to the intrinsic instability of the materials in alkaline media, no effect on the activity. Ni7Mo7, identified earlier as durable, proves to be highly unstable in the applied ADTs. The results show that the enhanced activity of unsupported bulk Mo–Ni electrodes can solely be ascribed to increased specific surface areas.

Molybdenum-nickel materials are catalysts of industrial interest for the hydrogen evolution reaction (HER). This contribution investigates the potential influence of ordered crystal structures on the catalytic activity. Well-characterized surfaces of the single-phase intermetallic compounds Ni7Mo7, Ni3Mo and Ni4Mo were subjected to accelerated durability tests (ADTs) and thorough characterization to unravel, whether crystallographic ordering affects the activity. Due to their intrinsic instability, molybdenum is leached resulting in higher specific surface areas and nickel-rich surfaces. The gain in surface area scales with the applied potential and the molybdenum content of the pristine samples. The nickel-enriched surfaces are more prone to form Ni(OH)2 layers, which leads to deactivation of the Mo-Ni materials. The crystal structure of the intermetallic compounds has, due to the intrinsic instability of the materials in alkaline media, no effect on the activity. The earlier as durable identified Ni7Mo7 proves to be highly unstable in the applied ADTs. The results indicate that the enhanced activity of unsupported bulk Mo-Ni electrodes can solely be ascribed to increased specific surface areas.

We demonstrate the systematic hardness enhancement of the CoCrFeNi high-entropy alloy (HEA) by the addition of tungsten carbide (WC). Mixed thin films are fabricated by magnetron co-sputtering using a home-made spark plasma-sintered CoCrFeNi target and a commercially available WC target. The WC content in the thin films is adjusted via the ratio of deposition powers applied to the targets. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) measurements were taken to determine the surface and bulk stoichiometry, respectively. The uniform distribution of the elements is confirmed via EDX mapping. X-ray diffraction (XRD) is carried out on the samples to determine the crystal phase formation. The Vickers hardness of the thin films is investigated using nanoindentation and shows an increase in the hardness in the thin films following an increased WC content. The data obtained are presented in comparison to pure WC and CoCrFeNi thin films fabricated by magnetron sputtering, respectively.

Compositional alterations to high-entropy alloys (HEAs) allow further evolution of these materials by adjusting their property profiles. This way, they can be used for coating technologies and surface-protection applications. In the present work, minor quantities of the non-metallic alloying constituents, BSiC, were added to the CrFeNi base system. The alloy development was carried out in an electric arc furnace in comparison with the nickel-based alloy Ni-600. With regard to the BSiC-free variant, the wear resistance can be significantly increased. The powder was manufactured by inert gas atomization and characterized, followed by processing via high-velocity oxy-fuel spraying (HVOF) and high velocity laser metal deposition (HS-LMD). Depending on the manufacturing conditions, the proportion and shape of the precipitates within the microstructure differ. Compared to both the reference system and the as-cast condition, the coating systems demonstrated comparable or improved resistance to wear. The evaluation of the process–structure–property relationships confirmed the great potential of developing load-adapted HEA systems using non-metallic alloy constituents in the field of surface engineering.