The investigation of the improved properties of N(+)-implanted amorphous bright chromium deposited (ABCD) electroplate

Amorphous bright chromium deposits (referred to as the ABCD method) offer significant improvement over conventional chromium electroplate in that they have fewer defects, have smoother surfaces, are more resistant to corrosion and are harder. The hardness of the ABCD electroplate can be significantly increased by various treatments such as annealing and N{dollar}sp+{dollar} implantation. This work investigates and compares the improvements obtained by N{dollar}sp+{dollar} implantation of ABCD electroplate with that of conventional chromium electroplate and correlates changes in hardness with structure and chemical properties. Implantation leads to increased hardness, but the extent is most pronounced for conventional films which were not annealed and ABCD films which were annealed at or below 400{dollar}spcirc{dollar}C for 1/2 h. Using Knoop hardness measurements in a differential manner, it was determined that the near surface region preferentially increases in hardness over the bulk of the electroplate after N{dollar}sp+{dollar} implantation. Implantation at high dosages results in the implantation region Cr being bound as CrN, oxides and nitrides with N displacing C in ABCD films. Increased dosages result in decreased N retention values while implanting at elevated temperatures increases the retained N, causes N to migrate more deeply into the bulk, and yields high hardness values. The effect of annealing ABCD N{dollar}sp+{dollar}-implanted films was also examined. A non-annealed film and a {dollar}600spcirc{dollar}C annealed film were N{dollar}sp+{dollar}-implanted and characterized using Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA or XPS) and X-ray diffraction (XRD). The annealed film is more highly crystalline than the non-annealed film. Diffraction lines due to Cr{dollar}sb7{dollar}C{dollar}sb3{dollar} and Cr{dollar}sb2{dollar}N are readily apparent. Auger electron spectroscopy and ESCA show that the film compositions are similar but that the chemical states of the surface species differ in that most of the organic carbon contained in the film is converted to carbide during annealing. These differences are responsible for the increase in Knoop hardness (1660 to 2980) derived from annealing the sample prior to implantation. In pre-annealed ABCD films, the ESCA, AES and XRD data show that the increased hardness is due to an enhanced crystallinity caused by annealing and the concurrent formation of Cr{dollar}rmsb7Csb3.{dollar} The N{dollar}sp+{dollar} implantation process itself apparently is not affected by the preannealing step. Conventional N{dollar}sp+{dollar}-implanted chromium films were also investigated using ESCA (or XPS), AES, depth profiling and ISS to provide a reference for comparison of ABCD electroplate.