Effect of coating thickness and deposition methods on the stripping rate of Cr–N coatings

Cr-N benefits from good oxidation and corrosion resistance, which has, until recently, caused difficulties in removing the coating without damage to substrates. Consequently, the industrial use of Cr-N coatings, particularly on expensive tools, has been limited. As a new commercially viable wet-stripping process has been developed that causes little or negligible damage to steel substrates, it is appropriate to investigate the effect of coating thickness and structure on the stripping rate of different Cr-N films. In this work, Cr-N coatings deposited by magnetron sputtering, arc and electron beam evaporation, having different thicknesses, were wet-stripped. The stripping rate was evaluated by statistical analyses for each deposition method and thickness. The stripping rate for the various deposition methods was correlated to the coating phases, structure, morphology, and surface roughness, which varied depending on the deposition process. For all deposition methods, the stripping rate was constant at a given as-deposited coating thickness. Regardless of the deposition method, the stripping rate for all different as-deposited thicknesses was statistically similar within the same deposition process, indicating that the stripping rate was independent of the coating thickness. Moreover, the stripping rate was not influenced by changes in the coating structure with increased thickness, which occurred in are and electron beam Cr-N coatings. For coatings having similar as-deposited thicknesses, the highest stripping rate was obtained in magnetron sputtered Cr-N (similar to 4.4 gin h(-1)), followed by electron beam and arc Cr-N coatings, which displayed similar stripping rates (similar to 3.3 gm h(-1)). The highest stripping rate recorded for magnetron Cr-N coatings could not be explained by changes in coating structure/morphology and surface roughness. The differences in the stripping were attributed to the amount of CrN phase present in the coatings. (c) 2005 Elsevier B.V. All rights reserved.