Effect of Particle Size and Morphology on Critical Velocity and Deformation Behavior in Cold Spraying

Experimental investigations, coupled with numerical simulations, reported in the literature have documented the effect of particle size quite systematically. However, similar systematic studies on the role of particle morphology are lacking in the literature, although numerous experiments suggest a qualitative dependence of the coating process on the morphology. In this paper, we attempt to address the lacunae by comparing the deformation behavior and critical velocity by systematically varying the particle morphology and size. We have considered two different shapes, viz., spherical particles (where the size has been varied) and conical particles (where the morphology has been varied as a function of the apical angle, in addition to varying the size). Equi-volume comparison between the spherical particles and conical particles with different morphologies allow us to establish quantitative dependence of deformation characteristics and critical velocity on the particle morphology. We demonstrate that the vertices in conical shapes are regions of high stress concentration and deform preferentially; furthermore, the larger the apical angle the more closely does the deformation behavior of the conical particles resemble the sphere. Therefore, a knowledge of the distribution of particle size and morphology is expected to help tune and optimize the processing conditions.