as high as 0.55 (i.e. N/Cr ratio over 1.2). At higher N/(Cr+N) atomic ratios, the coexistent state of solid solution with Cr2N nitride phase is relatively stable in a α-Cr large range of nitrogen concentrations (e.g. N/(Cr+N) ratios, from 0.18 to 0.55 in these PhD investigations), and can survive at relatively high temperature (e.g. 500 °C). With an atomic of Ag/(Cr+Ag) as low as 0.44 (other elements being the minority), an fcc-Ag matrix (with other elements in solid solution) would form. Moreover, fluctuations in Cr, Ag and Cu distribution in a scale of less than 5 nm was found, which could be beneficial in the precipitation of Cu and/or Ag as solid lubricants under moderately high temperature (e.g. 500 °C) service. The co-existence of Cu with Ag in a PVD metallic coating was found to be beneficial to Ag transport onto the coating surfaces, resulting not from the anticipated network channels’ of Cu, but from the much higher detachment rate of ‘intergranular Cu than Ag, which can a path’ for Ag to transport after Cu. Therefore by proper ‘leave design and processing, CrCuAgN coatings with appropriate elemental compositions and solid-solution matrix can be obtained, in which the precipitation rate of Ag can be partially controlled by the concentration of Cu (which does not need to be very high; 4.5 at.% Cu appears to be sufficient), resulting in the controlled supplement of solid lubricants to the coatings surface.
as high as 0.55 (i.e. N/Cr ratio over 1.2). At higher N/(Cr+N) atomic ratios, the coexistent state of α-Cr solid solution with Cr2N nitride phase is relatively stable in a large range of nitrogen concentrations (e.g. N/(Cr+N) ratios, from 0.18 to 0.55 in these PhD investigations), and can survive at relatively high temperature (e.g. 500 °C). With an atomic of Ag/(Cr+Ag) as low as 0.44 (other elements being the minority), an fcc-Ag matrix (with other elements in solid solution) would form. Moreover, fluctuations in Cr, Ag and Cu distribution in a scale of less than 5 nm was found, which could be beneficial in the precipitation of Cu and/or Ag as solid lubricants under moderately high temperature (e.g. 500 °C) service. The co-existence of Cu with Ag in a PVD metallic coating was found to be beneficial to Ag transport onto the coating surfaces, resulting not from the anticipated ‘intergranular network channels’ of Cu, but from the much higher detachment rate of Cu than Ag, which can ‘leave a path’ for Ag to transport after Cu. Therefore by proper design and processing, CrCuAgN coatings with appropriate elemental compositions and solid-solution matrix can be obtained, in which the precipitation rate of Ag can be partially controlled by the concentration of Cu (which does not need to be very high; 4.5 at.% Cu appears to be sufficient), resulting in the controlled supplement of solid lubricants to the coatings surface.