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Piston Ring Coatings

Cermet represent an important family of thermally sprayed wear-resistant coatings. Cermets are applied to the running face of the ring for highly loaded applications and consist of a mixture of metallic and ceramic compounds. The Cermet coatings prolong the lifetime of the ring package significantly, as shown in the graph. Daros offers a variety of different Cermet coatings. All Cermets are produced in-house with state-of-the-art plasma-spraying equipment. The coatings are always thoroughly tested in Daros' laboratory, ensuring world-leading performance.

Alucoat™ is a soft running-in coating applied to the ring's running face (arc-sprayed) in order to let the ring seal properly within the first few hours of operation (during shop-testing or after overhaul for marine engines).
Another function of the running-in coating is to gently finish the running surface on the cylinder liner during the first few hundred hours after installation of a new liner. The running-in coating is applied directly to the base material or in addition to a wear-resistant coating.

In order to make the bottom ring plane more resistant to wear, hard chromium is sometimes applied on the ring plane as well as the piston groove, in order to increase the TBO. Hard chromium is a well-tested technology providing excellent resistance to ring groove wear.
By hard-chrome plating the lower face, the surface structure becomes smooth and prevents the abrasive particles (ex. Catalytic fines) from being trapped, thereby reducing the ring groove wear.