MAGNETRON SPUTTER-DEPOSITION OF CHROMIUM DIBORIDE COATINGS

Chromium diboride has considerable potential as a protective coating f or materials exposed to wear and corrosion. A series of CrB2 coatings have been deposited on polished AISI 316L substrates by unbalanced mag netron 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 G Pa (approximately 4100-4700HK). Most of the deposition conditions prod uced coatings with a strong (001) orientation. By changing target-subs trate separation, pressure and bias, coatings with a (101) orientation could also be produced. CrB2 coatings with a (001) orientation afford ed excellent corrosion protection when exposed to 10 wt% FeCl3. No evi dence of localised corrosion was observed. Uncoated AISI 316L under th e same conditions showed extensive corrosion damage. CrB2 coatings wit h a (101) orientation offered less protection to 316L due to the forma tion of fractures that led to rapid attack of the underlying substrate . The CrB2 coatings markedly increased the wear resistance of AISI 316 L; but those coatings with a (001) orientation gave a more consistent improvement. (C) 1998 Elsevier Science S.A. All rights reserved.