Influence of thermal properties and temperature of substrate on the quality of cold-sprayed deposits

The properties of cold-sprayed deposits are often considered to depend mainly on the particle velocity and the particle temperature. The present paper demonstrates, through systematic experimentation and multi-scale modelling, that the substrate properties, too, influence the deposit properties, even in the regions far away from the substrate/deposit interface. Cold spraying experiments were performed with copper and titanium powders, using fixed process parameters, but different substrate materials and different substrate temperatures. As a measure of coating quality, the electrical conductivity of the coatings was evaluated on the top surface of (0.8-1 mm) thick coatings. The coating conductivity was found to depend strongly on the initial temperature and the thermal effusivity of the substrate. The mechanical properties of the substrate, also, influence the local coating properties, but only in the regions within 50 μm distance from the substrate/coating interface. The temperature and the thermal effusivity of the substrate control the instantaneous temperature of the top surface layer of the already deposited material, thus influencing the extent of particle bonding and the coating properties. These findings underline the role of thermal management in cold spraying.

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