| Abstract | The quality of cold sprayed copper coatings in the as-sprayed condition heavily relies on the characteristics of the feedstock powder. While previous studies have delved into the influence of particle velocity, size, and surface oxides on the quality of as-sprayed coatings, little attention has been paid to investigating the heat treatment responses of coatings with distinct initial characteristics. In previous work, the effects of particle velocity, size, and surface oxides on as-sprayed coating properties (i.e microstructural characteristics, mechanical properties and electrical conductivity) were investigated. Coatings with different as-sprayed quality were produced, ranked from “best” to “worst” as follows: Fine-4.9, Coarse-4.9 and Fine-2.1. The differences in properties were attributed to variations in the amounts of defects at the particle-particle interfaces (PPIs), caused by different process parameters (i.e gas pressure) and powder characteristics (i.e particle size) for each coating. The present study focuses on the subsequent heat treatment of these coatings under identical conditions (1 hour at 350 °C, under ambient atmosphere), to monitor the evolution of their microstructural characteristics, mechanical and electrical properties. The results show that in all cases, the ductility and electrical conductivity of the coatings generally improved with heat treatment. This is primarily attributed to the redistribution of surface oxides at the PPIs that improved the bonding between the particles. However, the bonding between the particles and properties of the Coarse-4.9 did not improve up to the levels of the Fine-4.9 and Fine-2.1, even though the latter exhibited much inferior properties in the as-sprayed condition. Microstructural analysis of the surface oxides at the PPIs of the, as-sprayed, Coarse-4.9, suggest that their higher thickness versus the other two coatings may have contributed to the retardation of sintering in that case. Finally, a correlation between the ductility, electrical conductivity and 3-D defect areal fraction for the heat-treated coatings is established. |
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