Functional electrolytic composite coatings Ni-SiC-PTFE
Benigna Szeptycka Instytut Mechaniki Precyzyjnej, ul. Duchnicka 3, 01-796 Warszawa
Quarterly No. 4, 2005 pages 72-77
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abstract Electrolytic composite coatings Ni-SiC-PTFE were obtained by electrodeposition from low-concentrated Watts electrolyte with SiC and PTFE dispergated by surface - active agents. Coatings were deposited on steel substrate (St3S) under galvanostatic conditions. Chemical composition of the coatings, determined by gravimetric and ICP spectrometry methods, depended not only on the content of the dispersed particles but also on the used surface - active agent (Tab. 1, Fig. 1). Obtained coatings contained from 0.8 to 8 vol.% of dispersed particles. The internal stress of deposited composite coatings, measured by dilatometric method, were comprehensive and at reach of the coating thickness ~30 μm approached to 0 (Fig. 2). The accelerated corrosion test of electrodeposited coatings Ni-SiC-PTFE in comparison with the technical chromium coating was carried out according to PN-EN ISO 4541 (corrosion test Corrodkote). All investigated coatings beared test for the heavy conditions and the hybrid coatings for the extremally heavy conditions (Tab. 4). The measurements on the Tester T-05 in the oscillating motion with lubrication were executed on the purpose to investigate the usability of the electroplated hybrid layers to work in the interconnection of slidings parts and assambles of motor vehicle working in the reciprocating or oscillating motion. In comparison to these the technical chromium coating was investigated. The two hybrid coatings showed more than twice as great wear resistance (Fig. 3) than the technical chromium coating. The friction coefficient of all investigated interconnections was low, between 0.095 ±0.02 (Fig. 4). Key words: nickel, composites, hybrid, electrodeposition, Ni-SiC-PTFE coatings, corrosion resistance, wear resistance, coefficient of friction