Diamond-like nanocomposite coatings for low-wear and low-friction applications in humid environments

Abstract

Diamond-Like Nanocomposite (DLN, Dylyn®) coatings are amorphous, hard and wear resistant coatings, deposited using a plasma-assisted CVD process. These coatings consist of two interpenetrating networks, one being a diamond-like carbon (a-C:H) network and the other a glass-like a-Si:O network. This specific structure leads to lower internal stress, better adhesion and higher temperature stability as compared to diamond-like carbon. The structure and bonding type were investigated using grazing-incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS), respectively. The coefficient of friction of Diamond-Like Nanocomposites, as measured in a standard ball-on-disk tribometer using a steel counterbody, is typically 0.04 to 0.08 in air of 50% relative humidity (RH). Even in humid air of 90% RH and under water, the coefficient of friction stays below 0.1. The wear factor of Diamond-Like Nanocomposite coatings was determined using profilometric measurements of the wear track after a ball-on-disk test and is typically 2×10 −7 mm 3/N m. Under water, an extremely low wear factor, below 5×10 −8 mm 3/N m, was measured. This low-friction and low-wear behaviour of Diamond-Like Nanocomposite coatings, also in humid environments, enables industrial applications of these coatings as hard, self-lubricating coatings on sliding parts in the automotive, chemical, pharmaceutical or biomedical industry.