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JTTEE5 21:1046–1053 DOI: 10.1007/s11666-012-9778-6 1059-9630/$19.00  ASM International

Cold Spraying Activation Using an Abrasive Admixture S. V. Klinkov and V. F. Kosarev (Submitted January 16, 2012; in revised form March 2, 2012) In the present study, on the basis of a two-probability model we theoretically analyze the influence of surface erosion and activation due to abrasive particles impacting on the substrate (coating) surface on the total deposition efficiency of a sprayed mixture of abrasive and metal particles. Relations for the total deposition efficiency derived with regard to the activation effect due to abrasive particles were obtained. In the experiments, the deposition efficiency was measured as a function of the abrasive (SiC) concentration in the initial mixture with copper powder, the size of the abrasive particles, and the working-gas (air) stagnation temperature. Modeling data are compared to the present and previously published experimental data, and a good agreement between the data is shown.

Keywords

abrasive admixture, activation, cold spray, deposition efficiency, surface erosion

1. Introduction Experiments show (see, e.g., Ref 1-3) that in a cold spray deposition process involving a metal-abrasive powder mixture the deposition efficiency can exhibit an anomalous behavior as a function of the abrasive content of the mixture. Instead of the expected decrease of deposition efficiency due to the dilution of the metal powder with the abrasive particles, this efficiency in some cases was found to show an increase. Note that this phenomenon was observed under many different conditions: in low-pressure cold spray process (Ref 1, 2), in highpressure cold spray process (Ref 3), in spraying of preliminarily mixed powders or unprepared mixtures (when the components were mixed during their motion inside the prechamber/nozzle unit), during acceleration of spray flows in de Laval or ejector nozzles and also in alternating spraying of metal and abrasive particles on the same surface area. Here, the most typical powder materials are: metals (copper and aluminum) and abrasives (silicon carbide and alumina). The phenomenon of interest can be attributed to the fact that the abrasive particles, as they impact onto the substrate (coating) surface, activate this surface, thus promoting the adhesion of metal particles to it. The involvement of a surface activation process into the phenomenon of interest has found additional confirmation in experiments with mechanical pretreatment (sand blasting and grinding) of the surface (Ref 4). Moreover, S.V. Klinkov and V.F. Kosarev, Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of Russian Academy of Sciences (ITAM SB RAS), Novosibirsk, Russia. Contact e-mail: [email protected].

1046—Volume 21(5) September 2012

the existence of an induction period for deposition, which was attributed to preparation of the surface by the metal particles themselves during the spraying process, also points to the involvement of an activation process in th