Sliding wear behavior of diamond-like nanocomposite coatings

Diamond-like nanocomposites (DLN) are a class of amorphous thin film material consisting of a diamond-like carbon (a-C:H) network and a glass-like a-Si:O network. The sliding wear behavior of 1-2-mu m-thick DLN coatings on Si was studied using WC and steel balls in ambient air (RH = 30-50%) at initially high contact stresses (0.8 GPa). The hardness of the DLN coatings, 9-17 GPa, was greater than that of steel (8 GPa) but less than that of WC (16 GPa). The friction coefficients for both couples were between 0.04 and 0.06, and the endurances were from 30000 to 200000 cycles. Despite the similarities, the wear behavior of the steel/DLN and WC/DLN couples differed: in the former, the steel balls wore, producing lower stresses but wider and deeper wear tracks; in the latter, the WC ball did not wear, and the wear tracks were narrower and wore uniformly. The latter wear behavior allowed wear rates for DLN to be determined. The wear of the DLN was measured at regular intervals during extended ball-on-disk testing. DLN was shown to wear at a constant rate, i.e. linearly with number of cycles, and to have wear factors in the range of 2 x 10(-8)-1.1 x 10(-6) mm(3) N-1 m(-1). (C) 1999 Elsevier Science S.A. All rights reserved.