By means of In-Mold-Metal-Spraying (IMMS), wire arc sprayed metal coatings are transferred onto plastic parts during the injection molding process for the efficient production of metallized plastic parts. One potential field of application of IMMS parts are electrical applications such as electrically conductive tracks or electromagnetic shielding. In the current study, the properties of the transferred coatings, especially the electrical resistivity, are determined. Different feedstock materials are used for the application of the coatings. In the first investigation, pressurized air is used as atomizing gas for wire arc spraying. In contrary to Zn coatings, Cu coatings applied with pressurized air have a significantly higher electrical resistivity in comparison to massive copper. One possible reason for this is the oxidation of the Cu particles during the spraying process. Therefore, N 2 and a mixture of N 2 and H 2 are used as atomizing gas to reduce the oxidation of particles. Consequently, the electrical resistivity of IMMS parts can be significantly reduced. Furthermore, spraying distance, current and pressure of the atomizing gas are varied to investigate the influence of these process parameters on the coating properties.

A new process called in-mold metal spraying (IMMS) shows good potential for producing metallized plastic parts quickly and inexpensively. A zinc layer is deposited on mold cavity inserts using wire arc spraying and subsequently transferred to a plastic carrier via injection molding. Finely adjusted bonding strength between the carrier body and coating is essential for successful coating transfer. To that end, this study evaluates the influence of carrier body surface pretreatments on the transferability and bonding strength of zinc coating. Carrier bodies made of different types of steel pretreated by glass bead blasting and EDM were tested and their surface topography examined. In the initial experiments, the hardness and surface topography of carrier bodies were identified as factors that can influence coating transferability. Further experiments focusing on the adhesion strength of zinc on hardened and annealed carrier bodies were conducted to verify the influence of hardness on bonding strength.

Nano-sized, micro-sized, and bimodal Cr 3 C 2 -25NiCr feedstock powders were prepared using a spray drying and agglomeration sintering process and deposited by HVOF spraying. The microstructure and phase composition of the three powders and corresponding coatings were assessed along with coating hardness, toughness, and abrasive wear resistance. All three powders were nearly spherical in shape, but the bimodal powder had the best sphericity, the most uniform composition distribution, and the highest deposition efficiency. All three coatings were primarily composed of Cr 3 C 2 and NiCr phases, although a small amount of Cr 2 O 3 was detected in the nano- and micro-coatings due to oxidation. Compared with the micro-coating, the nano-coating has higher toughness but lower microhardness and abrasive resistance. The bimodal coating, however, integrates the advantages of the other coatings, has low porosity and a dense microstructure, and is tightly adhered to the substrate, thus displaying the best comprehensive performance.

In thermal spraying uncoated substrates usually require roughening. As the most common roughening method, grit blasting increases the surface area and produces undercuts, which facilitate mechanical interlocking and thus promote the bonding between the substrate and coating. The effects of grit blasting parameters, i.e. the particle size, the blasting angle, the stand-off distance and the pressure, on the resulting surface topography are investigated. Furthermore the efficiency and wear behavior of the blasting media are analyzed. Influences of three different blasting media, corundum, alumina zirconia and steel shot, on the surface roughening are compared.

The pore structure in nano-porous TiO 2 coating influences the ion diffusion property and photovoltaic performance of dye-sensitized solar cells (DSC). In this paper, TiO 2 coatings were deposited by vacuum cold spray (VCS) using a strengthened nanostructured powder. The pore structure, ion diffusion and dye infiltration properties were examined to understand the deposition mechanism of the coating and the suitability of cold sprayed TiO 2 coating for DSC. It was interestingly found that the pores in the VCS TiO 2 coating presented a bimodal size distribution with two peaks at ~15 nm and ~50 nm, which contributed to a much higher ion diffusion coefficient comparing to that of the conventional unimodal-sized nano-porous coating. The dye infiltration and loading are beneficial from the bimodal size distribution of the pores. Based on the impact behavior of the spray powder, a deposition model was proposed to explain the deposition mechanism of the strengthened nanostructured powder during vacuum cold spray.