Nikasil

Nikasil is a trademarked electrodeposited lipophilic nickel matrix silicon carbide coating for engine components, mainly piston engine cylinder liners.

Nikasil was introduced by Mahle in 1967, initially developed to allow rotary engine apex seals (NSU Ro 80, Citroën GS Birotor and Mercedes C111) to work directly against the aluminium housing. This coating allowed aluminium cylinders and pistons to work directly against each other with low wear and friction. Unlike other methods, including cast iron cylinder liners, Nikasil allowed very large cylinder bores with tight tolerances and thus allowed existing engine designs to be expanded easily. The aluminium cylinders also gave a much better heat conductivity than cast iron liners, an important attribute for a high-output engine. The coating was further developed as a replacement for hard-chrome plated cylinder bores for Mercury Marine Racing, Kohler Engines, and as a repair replacement for factory-chromed snowmobiles, dirt bikes, ATVs, watercraft and automotive V8 liners/bores.

Nikasil is short for Nickel Silicon Carbide. Silicon carbide is a very hard ceramic (much harder than steel) that can be dissolved in nickel. The nickel solution can then be electroplated onto the aluminium cylinder bore. The piston rings will then rub off the exposed nickel, leaving a very hard layer of silicon carbide to protect the aluminium piston from direct contact with the aluminium cylinder. With this setup, the engine tolerances can be much tighter for better performance. The cylinder must be re-plated after it is re-bored, but Nikasil is extremely durable, so the cylinder does not need to be reworked as often as an iron or chrome cylinder.

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