Microstructure evaluation of cold-sprayed copper coatings by EBSD

Abstract

The cold spray technique is a new coating technology that is based on the high velocity impinging of small solid particle on the substrate. This technique allows to produce coatings and thick deposit with less heat influence. Cold-sprayed coating indicates brittle fracture that a crack is propagated in particle interface. It is important to understand and control the microstructure. This study evaluates the microstructure and heat treatment behavior of the cold-sprayed copper coatings by SEM and EBSD (Electron Back-Scatter Diffraction) method. CI (Confident Index)and IQ (Image Quality) values of EBSD method was applied to the evaluation of crystal structure and grain boundary structures. It was found that cold-sprayed coating annealing does not complete with standard annealing conditions such as applied to the bulk material. As-sprayed coating consists of fine grains. The grains are surrounded by irregular atomic arrangement region and amorphous phase. Grain boundary and particle to particle interface are inhomogeneous. Since this irregular interface structure role diffusion barrier, heat treatment effects of cold-sprayed coatings are different from bulk materials. Moreover, it is considered that structure is possible cause of brittle fracture.