Ti-containing and W-containing diamond-like hydrocarbon coatings have been synthesized by glow discharge reactive magnetron sputter deposition in an Ar/CH4 mixture. it is shown that these metal-containing hydrocarbon coatings consist of nanocrystalline TiC and WC embedded in an amorphous hydrocarbon matrix and are thin-film nanocomposite materials. The elastic modulus and hardness of these nanocomposites exhibit systematic dependence on their composition, while the ratio of hardness to modulus remains approximately a constant. It is also shown that the elastic modulus and hardness of these nanocomposites are within macromechanical bounds for two-phase composite materials.
High-pressure cold spray process is a relatively new coating process that uses high-velocity powder particles to form coatings. One of the requirements for this process is to inject the particles to be sprayed into a prenozzle chamber where both the particles and the powder feed gas are entrained into the primary gas stream. In this study, we investigated the effects of powder injection on coating formation through both experimental studies and computational simulations. Several issues related to powder injection will be examined, including the size of powder injector, the differential pressure, powder gas flow, and injector clogging. It is shown that an improved powder injector design not only enables the use of reduced amount of powder carrier gas flow but also maintains steady, clogging-free spraying conditions. Combining with properly selected injection conditions, it can also lead to enhanced coating deposition by kinetic spray process.
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