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Laser-clad AlCrFeCoNi high entropy alloy (HEA) coatings, produced on the surface of AISI 316 L stainless steel, were pack-borided at 1000 °C for 4 h in open air, high-purity Ar and vacuum environments. The HEA, which had an initial hardness of 6.14 ± 2.06 GPa, formed a complex boride layer consisting of (CoFe)B2, (CrFe)B2 and Cr2Ni3B6 phases on its surface, with hardness ranging from 15.95 ± 0.7 to 20.15 ± 4.50 GPa as a result of the boriding process. While the greatest boride layer thickness was obtained in the sample borided in vacuum, the highest surface hardness was obtained in the sample borided in air. The borided coatings showed improved wear resistance and lower friction values compared to the untreated control samples, both at 25 °C and 650 °C. The borided coatings also showed reduced coefficients of friction at 650 °C. The wear losses at 650 °C significantly exceeded those at 25 °C.

There are various opportunities to improve the adhesion between polymer and metal in metal-plastic composites. The addition of a bonding agent which reacts with both joining components at the interfaces of the composite can enhance the bonding strength. An alternative method for the adjustment of interfaces in metal-plastic composites is the specific surface structuring of the joining partners in order to exploit the mechanical interlock effect. In this study the potential of using an adhesion promoter based on twin polymerization for metal-plastic composites in combination with different methods of mechanical surface treatment is evaluated by using the tensile shear test. It is shown that the new adhesion promoter has a major effect when applied on smooth metal surfaces. A combination of both mechanical and chemical surface treatment of the metal part is mostly just as effective as the application of only one of these surface treatment methods.