The microstructure of Cu-Cr composite coatings produced by detonation spraying and their behavior under arc erosion conditions

Cu-Cr composites are extensively used as electrical contacts in vacuum circuit breakers due to their favorable electrical and mechanical properties. In this study, Cu-Cr composite coatings were formed on copper substrates by detonation spraying. Powder mixtures with chromium content ranging from 25 to 67 wt% were employed for the spraying process, and a pure copper coating was also prepared as a reference material. The microstructure and composition of the coatings were characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis. The performance of the coatings was assessed through arc erosion testing, and the post-test surface topography of the samples was analyzed via optical profilometry. TEM analysis revealed the presence of nanoscale copper oxides in the pure copper coatings and chromium oxides in the Cu-Cr coatings, respectively. The detonation-sprayed Cu-Cr coatings exhibited high hardness (240 ± 10 HV) and adhesive strength (45 ± 10 MPa), coupled with low porosity (< 1 %). The electrical conductivity of the coatings varied between 25 and 41 % IACS, depending on the chromium content. Notably, coatings with a chromium content of 33–43 wt% exhibited no surface protrusions after arc exposure, indicating superior resistance to arc-induced damage.