Influence of nozzle velocity and powder feed rate on the coating mass and deposition efficiency in cold spraying

Abstract

The subject matter of the present study is the dependence of coating mass and deposition efficiency on the velocity of the nozzle motion with respect to the substrate and, to a degree, the dependence of these characteristics on the powder feed rate at all other parameters remaining unchanged. Experimental results obtained in the present work show that the deposition efficiency non-monotonically depends on the nozzle traverse velocity. There exists an optimum nozzle traverse velocity at which the deposition efficiency is maximal. Both on increase and decrease of nozzle traverse velocity, the deposition efficiency diminishes. There exists a critical (maximum) nozzle traverse velocity at which the deposition efficiency vanishes. The most important factors affecting the spraying process are identified; these are: (i) the involvement of an initial latent stage in the process and (ii) the variation of the impingement angle of particles. With allowance for those factors, we have proposed, for the first time, a model for estimating the coating mass and deposition efficiency as functions of nozzle traverse velocity and powder feed rate. This model provides a good qualitative description to experimental results.