Tribological Properties of Multi-Layer a-C:H:W/a-C:H PVD-Coatings Micro-Structured by Picosecond Laser Ablation

Abstract

An increase of the service life of tribological systems subjected to dynamic-mechanical loads is important for numerous mechanical applications. The present study deals with the impact of several micro-structured surface topographies of graded Cr/CrNx/(Cr,W)Cy/a-C:H:W/a-C:H PVD hard coatings on their friction and wear behavior. The coatings were applied by reactive magnetron sputtering on a hardened 1.2379 steel substrates and subsequently micro-structured by laser ablation using a picosecond laser. Pin-on-disc tests were carried out against aluminum under both oil lubrication and dry conditions. The diameters of the micro-dimples were varied between 50 μm, 100 μm and 150 μm at a constant degree of coating coverage of about 60 %. The coefficients of friction and wear were determined after 20,000 cycles by confocal laser-scanning microscope (CLSM), scanning electron microscopy (SEM) and by energy-dispersive X-ray spectroscopy (EDX) to analyze possible transfer layer formations.