Effects of Surface Oxidation of the Feedstock Materials on the Cold Sprayed Al Coating Quality and Properties

Unlike TS where the feedstock material changes microstructurally and chemically to a large extent during spraying, CS technique tend to preserve the characteristics of the feedstock powder. This makes the selection of feedstock materials a critical factor in depositing cold-sprayed coatings. The objective was to investigate the influence of the oxide shell of Al particles on the coating building-up, quality, adhesion to substrate, and particles cohesion, following the spraying of Al feedstock with different levels of oxygen content (artificially oxidized). Using different analytical tools such HRTEM, XRD, IGF, and DSC, microstructure, chemical, and phase analysis were conducted to assess the feedstock and the coatings. It was found that the DE decreased as oxygen content increased. Above a certain level of oxide phase,the sprayed Al particles start to bounce-off and it became difficult to build-up, and thus the minimum acceptable oxygen content within Al coating was determined. It is believed that due to the high hardness and the microstructure nature of the oxide, oxide shells surrounding the Al particles influences the particle deformation behavior during impact and its cohesion nature. In addition, the accumulation of the oxide debris between at Al particles interface hinder the intimate contact between the metallic particles.