Investigation on the nanostructure of as-deposited and post-coat annealed CrCuAgN PVD nanocomposite coatings

CrCuAgN coatings with a wide range of Cu and Ag contents (combined values in the range of <10 at% to >50 at%) were prepared on AISI316L stainless steel coupons by closed-field unbalanced magnetron sputtering(CFUBMS). After the deposition process, the coated coupons were annealed at 300 °C and 500 °C, respectively. The transport behaviour of Cu and Ag in selected CrCuAgN coatings was then investigated by conventional and high-resolution transmission electron microscopy (HR/TEM), energy-filtered (EF)TEM elemental mapping, and scanning (S)TEM with EDX elemental mapping. Results showed that the aggregation of both Cu and Ag are detachment-limited, rather than diffusion-limited. The co-existence of Cu with Ag in a PVD metallic coating was found to be beneficial in promoting Ag transport to the coating surface, resulting not from the anticipated “intergranular network channels” of Cu, but from a much higher detachment rate of Cu than Ag. This study verified that CrCuAgN coatings with desired composition and nanostructure can be obtained via coating/process design, providing controllable precipitation rate of Ag (via adjusting Cu content) for practical applications.