Grinding wheels are usually manufactured by powder metallurgical processes, i.e. by moulding and sintering. Since this requires the production of special moulds and the sintering is typically carried out in a continuous furnace, this process is time-consuming and cost-intensive. Therefore, it is only worthwhile for medium and large batches. Another influencing factor of the powder metallurgical process route is the high thermal load during the sintering process. Due to their high thermal sensitivity, superabrasives such as diamond or cubic boron nitride are very difficult to process in this way. In this study, a novel and innovative approach is presented, in which superabrasive grinding wheels are manufactured by thermal spraying. For this purpose, flat samples as well as a grinding wheel body were coated by low-pressure (LP) cold gas spraying with a blend of a commercial Cu-Al2O3 cold gas spraying powder and nickel-coated diamonds (8-12 μm). The coatings were examined metallographically in terms of their composition. Afterwards, the grinding wheel was conditioned for the grinding application and the topography was evaluated. This novel process route offers great flexibility in the combination of binder and hard material as well as a costeffective single-part and small-batch production.

Metal structures in offshore facilities are usually protected from corrosion using Zn-Al coatings even though they are subjected to collective stress conditions. This paper evaluates a post-treatment called machine hammer peening and its effect on surface finish, induced residual stresses, and near-surface microstructure of thermally sprayed ZnAl4 coatings. As expected, coating roughness was reduced from about Rz = 53.5 μm in the as-sprayed condition to 10.4 μm after treatment and coating densification was revealed in the near-surface zone. Residual stresses, which were surprisingly compressive in the as-sprayed condition, were likewise affected by the peening process, reaching a maximum of 200 MPa. The influence of peening direction and other such parameters were also investigated as part of the study.

Despite their excellent specific mechanical properties magnesium-based alloys are not widely used in the industry due to their high affinity to oxygen. Given the need for lightweight design, there are increasing efforts to replace high density materials by magnesium. One way to cope with the high oxygen affinity of magnesium is the use of thermally sprayed anti-corrosion coatings. However, conventional thermal coating processes have various process-related limitations. A case in point is coating of complex geometries and internal coatings with small diameters that often cannot be realized by conventional processes. Due to the changed process order some of the limitations of conventional coating methods can be resolved by the transplantation of thermally sprayed coatings. This method is a composite casting process for the coating of die cast components, where the thermally sprayed coating is applied to the corresponding area of the mold prior to the casting process. The aim of this study is to compare the effectiveness of transplanted thermally sprayed coatings with corrosion protection properties to conventional coatings deposited by thermal spraying and to discuss the ramifications with respect to industrial applications.

Automotive, aerospace, and energy applications demand for reliable coating systems to enhance the operating efficiency and the lifetime of processes, machines, and components. HVOF sprayed WC-CoCr coatings are commonly used, especially for wear resistant applications. Due to their high hardness and adapted corrosion resistance WC-CoCr coatings show perfect preconditions for highly stressed tribological systems. However, dynamic loads, caused by vibrations, alternating temperatures or cycling are challenging issues. Fatigue cracking and delamination can occur, resulting in fatal damage of the coated component. Therefore, crack and fatigue resistant high performance coatings are needed. In this research work, the influence of the substrate pre- and post-treatment (grit-blasting and micro-finishing) on the fatigue behavior of warm sprayed WC-CoCr is investigated. It was determined that the fatigue behavior of the applied coating can be improved by micro-finishing. The smooth surface structure results in a low interface roughness. This significantly reduces notching effects under load and enhances the fatigue strength of the specimen.

Be it to save the environment or to save money, engineers everywhere attempt to use materials which can’t normally withstand the surface stress they will be exposed to on their own. This is one of the reasons for the constant interest in new and innovative coating technologies. One such innovation is the transplantation of thermal sprayed coatings. In the transplantation process the coating is integrated into a high-pressure die casting process. In contrast to the conventional process chain, the coating is not directly applied to the work piece, but to a mold insert. During the pressure casting the melt infiltrates the coating and thus creates a join. This way the coating is indirectly applied to the die-cast work piece after removal from the mold. Additionally, depending on the materials involved, a material bonding connection similar to brazing is possible and results in an increased adhesion of the coating. A potentially very interesting trait of the transplantation process is, turning an internal coating process into an external coating process. This allows the coating of inside diameters well below the usual limit of an internal spray gun. Due to the high geometric accuracy of the process this can be potentially done without any need for additional finishing steps.

Manufacturing a die-cast workpiece with a thermal spray coating usually requires multiple steps. An alternative approach demonstrated in this study integrates the spray process into a high-pressure die casting step, eliminating the need for surface preparation and post processing of the coating. To achieve this, the coating is applied to a mold insert rather than the workpiece. During pressure casting, the melt infiltrates the coating and thus creates a joint. Depending on the coating and substrate, a bonding connection similar to brazing is possible. The ability to manufacture coatings this way makes it possible to coat inside diameters well below the limit of an internal spray gun.