Magnetron sputter deposition of chromium diboride coatings

Chromium diboride has considerable potential as a protective coating for materials exposed to wear and corrosion. A series of CrB2 coatings have been deposited on polished AISI 316L substrates by unbalanced magnetron sputter deposition at temperatures below 200 degrees C. All of the coatings were fully crystalline with thicknesses ranging from 2.6 to 6.1 mu m. The hardness of the coatings were in the range of 42-49 GPa (approximately 4100-4700HK). Most of the deposition conditions produced coatings with a strong (001) orientation. By changing target-substrate separation, pressure and bias, coatings with a (101) orientation could also be produced. CrB2 coatings with a (001) orientation afforded excellent corrosion protection when exposed to 10 wt% FeCl3. No evidence of localised corrosion was observed. Uncoated AISI 316L under the same conditions showed extensive corrosion damage. CrB2 coatings with a (101) orientation offered less protection to 316L due to the formation of fractures that led to rapid attack of the underlying substrate. The CrB2 coatings markedly increased the wear resistance of AISI 316L; but those coatings with a (001) orientation gave a more consistent improvement. (C) 1998 Elsevier Science S.A. All rights reserved.