AHC Oberflächentechnik GmbH: Coating to increase the friction of coupling sleeves in wind turbines

Kerpen,2011-05-13 Electroless nickel plating by the DURNI-COAT® process of AHC Oberflächentechnik GmbH creates wear-resistant surfaces on metal components. In the coating process, a nickel-phosphorus alloy is deposited, forming a strong bond with the surface. The coating process takes place in an aqueous electrolyte containing dissolved nickel ions. A reducing agent supplies the phosphorus, which is evenly integrated into the nickel coating. The deposition of the alloy is based on a chemical reaction, so no external current source is needed. This electroless process, unlike galvanic plating, produces a contour-true reproduction of the surface with the same layer thickness throughout.

For this process there is a coating variant for increased surface friction which is used in the wind turbine sector. SIC-9-DURNI-DISP is a DURNI-COAT® layer about 7 μm thick, into which silicon carbide particles with a grain size of about 9–12 μm are uniformly and homogeneously embedded. The coating is free of lead and cadmium. The SiC particles project out of the electroless nickel matrix. In a force-fit connection, the hard, sharp-edged particles bite into their counterpart, leaving depressions on its surface. Connecting elements coated with SIC-9-DURNI-DISP for increased surface friction can be used wherever a force transfer effect is required.

Coupling sleeves of copper bronze are coated with this variant. In the rotor of a wind turbine, the coupling sleeves are fitted in a friction clutch or overload unit. The coating serves to increase the coefficient of friction for the transmission of greater transverse forces or for the prevention of relative movements between the sleeve and the generator shaft.