Effect of reinforcement particles on cold-sprayed Al-based coatings

Abstract

In this study, malleable and heavy Ta particles were introduced into soft Al powders to prepare Al-Ta composite coatings through a low-pressure cold-spray process; for comparison, Al-A 2 O 3 composite coatings were also deposited. The surface and cross-sectional morphologies, deposition efficiency, microstructure, hardness and composition of the coatings were investigated. The results demonstrated that the Al-Ta coatings had roughness values that were almost twice as large as those of the Al-Al 2 O 3 coatings for the same volumetric fraction of reinforcement particles used in the feedstock. Ta particles were more effective in improving the deposition efficiency and densification than were Al 2 O 3 particles. The formation mechanism of the Al-Ta coatings was mainly attributed to the malleable and heavy nature of Ta particles, which allowed them to bond with the formed coating and impact the coating strongly through the peening effect.

Optimization of cold spray process parameters to maximize adhesion and deposition efficiency of Ni+Al2O3 coatings

“…The latter, when in contact with previously adhered powder particles, additionally deforms them, reduces the number and size of pores in the coating, and increases the adhesion and cohesion strength [26]. In addition, solid particles of Al 2 O 3 , before the formation of the coating, activate, destroying and removing the oxide layer on it, and increasing the surface roughness [27]. Activation of the surface means its cleaning and preparation before the coating begins to grow by repeated interaction of the first particles in the first seconds of exposure to two-phase flow to the surface.…”