A method for characterizing the degree of inter-particle bond formation in cold sprayed coatings

The degree of bonding between particles within cold-sprayed deposits is of great importance as it affects their mechanical and physical properties. This article describes a method for characterizing the bonding between aluminum and copper particles following deposition by cold spraying. Aluminum and copper powders were blended in the ratio 1:1 by volume, deposited onto a copper substrate and subsequently heat treated at 400 degrees C for 15 min. An intermetallic layer formed along some regions of the aluminum-copper boundaries, believed to be where true metal to metal contact had occurred. In other regions, metal to metal contact was inhibited by the presence of oxide films. Image analysis was employed to measure the fraction of the aluminum-copper interface covered with intermetallic phases and to estimate intermetallic thicknesses. By increasing the primary gas pressure in the cold-spray process, an increase in the degree of inter-particle bond formation was observed.