Abstract: Solid particles of primarily hard substances, solid lubricants, ductile metals or their alloys and/or molten polymers are embedded in a network of cracks of hard chromium coatings to attain improved physical characteristics, primarily to increase wear resistance, sliding behavior, ductility and corrosion resistance.The chrome plating process takes place in a microcrack-forming chrome-plating electrolyte with solid particles dispersed therein and with one-time or repeated current reversal so that, if the workpiece is connected to the anode, the network of microcracks in the chromium coating is widened and solid particles are embedded within the cracks. Preferred uses are as coatings on the bearing surfaces of piston rings or cylinder bearing sleeves for internal-combustion engines.

Abstract: Friction-reducing coating compositions and coated machine parts having a wearing surface provided with coatings of same. In one embodiment, the coating composition includes from 10 to 25 weight % molybdenum metal; from 55 to 70 weight % nickel alloy; and from 5 to 25 weight % chromium carbide Cr.sub.3 C.sub.2. In a second embodiment, the coating composition includes from 25 to 45 weight % molybdenum metal; from 45 to 60 weight % nickel alloy; and from 5 to 25 weight % of a hard substance selected from chromium metal, chromium carbide Cr.sub.23 C.sub.6 and molybdenum carbide Mo.sub.2 C. Preferably the nickel alloys contain from 73 to 95 weight % nickel and have a melting point below that of nickel metal. Preferably the friction-reducing coating is applied to a wearing surface by plasma flame spraying. These coatings impart excellent wear resistance to the wearing surface, while lowering wear of counter-running faces.

Abstract: A sprayed-on wear-resistant coating which is carried on a substrate constituted by a machine part surface, has an inner face oriented towards the substrate and an outer face oriented away from the substrate. The coating consists of a material whose structure and/or composition continuously varies from the inner face of the coating towards the outer face thereof.