New insights into the in-process densification mechanism of cold spray Al coatings: Low deposition efficiency induced densification

doi:10.1016/j.jmst.2018.09.045

Abstract

Abstract:

This work details new insights into the in-process densification mechanism of cold spray Al coatings. The results show a trend counter to common observations: coating plastic deformation levels and coating density decreases with an increase in particle impact velocity. A lower particle impact velocity and the consequent lower deposition efficiency (DE) results in greater tamping energy per unit volume of deposit, which is the primary reason for the observed trend. This is the first time that DE has been shown to have a non-linear impact on the density of a cold spray coating, with particle in-process tamping being the primary mechanism for coating densification.

Key words: Coating, Hardness test, Plastic deformation, Tamping

Richard Jenkins, Shuo Yin, Barry Aldwell, Morten Meyer, Rocco Lupoi. New insights into the in-process densification mechanism of cold spray Al coatings: Low deposition efficiency induced densification[J]. J. Mater. Sci. Technol., 2019, 35(3): 427-431.

Figures/Tables 4

Fig. 1. Cross-sectional SEM images of seven characteristic coatings showing a porosity variation trend with particle impact velocities of 640?m/s (a), 700?m/s (b), 730?m/s (c), 770?m/s (d), 840?m/s (e), 940?m/s (f), 1000?m/s (g).

Fig. 2. Coating relative density and DE against particle impact velocity (a), coating hardness and DE against article impact velocity (b) with 95% confidence interval error bars for relative density and hardness.

Fig. 3. Etched cross-sectional images (a-c) and their binary mode (d-f) of coatings produced at particle impact velocity of 640?m/s (a, d), 770?m/s (b, e) and 1000?m/s (c, f). The relative densities of the three coatings are 99.18%, 95.86% and 98.51%, respectively.

Fig. 4. Eprimary and Esecondary against particle impact velocity (a), Eprimary and Esecondary (single) against the particle impact velocity (b), and Etotal and DE against the particle impact velocity (c). The plastic strain distribution within the particle and coating upon impact at three typical impact velocities were also included in Fig. 4(b). A dotted-line divides High-DE/high-velocity and low-DE/low-velocity zones in Fig. 4(c).

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