Measuring Nikasil® coatings on aluminum automotive cylinders

Automotive cylinders are subject to extreme mechanical wear. A way of protecting aluminum cylinders is to plate the contact surfaces with Nikasil®, a hard coating technology used to improve the tribological characteristics of the cylinder parts and to optimize the heat transfer. It is often used for high-end engine components of premium car brands and in motor sports.

Nikasil® (from the German for Nickel-Carbide-Silicon – Nickel-Karbid-Silizium) is an electroplated nickel matrix with embedded silicon-carbide particles. Its amazing tribological characteristics make Nikasil® the ideal contact surface for pistons and rings; it is therefore used on high-end engine parts to minimize the friction within the engine block. The Nikasil® coating is appropriate for two- and four-stroke aluminum cylinder walls or sleeves and is used in a variety of automotive engines ranging from classic cars to the latest Formula 1 vehicles.

Fig. 1: Cylinder block made of aluminum coated with Nikasil®. Coating thickness approx. 20 - 50 µm

In practical use the cylinder walls or sleeves are electroplated with a layer of Nikasil®, typically between 80 and 180 µm thick. Afterwards, the coating thickness is controlled using the custom-configured table-top FISCHERSCOPE® MMS® PC2, further outfitted with a NICKELSCOPE® module and the probe ENW3. Overall, this specialized instrument employs the magnetic measurement method (hall effect).

In the next step the cylinder barrels are milled and honed to improve their sliding characteristics. A final coating thickness somewhere in the range of 25 to 50 µm is aimed for, which requires extremely narrow tolerances to be met in the measurement procedure.

Fig. 2: FISCHERSCOPE® MMS® PC2

The probe ENW3 is the centerpiece of the measurement system and is used both after the electroplating process as well as after honing. Its angled form helps the user to reach even difficult-to-access places.

Measuring inside cylinder barrels or sleeves can also be automated. To this end, the FISCHERSCOPE® MMS® PC2 can be equipped with a digital I/O module to control up to six probes at once; measurement values are collected and transferred to the instrument simulta­neously, making it possible to take multiple measurements with high frequency for quality control purposes in a running production line.

For precise thickness measurement of Nikasil® coatings the FISCHERSCOPE® MMS® PC2 – equipped with the NICKELSCOPE® module and the ENW3 probe – is the perfect choice for professional quality monitoring of Nikasil® coatings. Even automated measurements with multiple probes are feasible. Please contact your FISCHER representative for more information. 

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Chembo Overfladeteknik A/S.
Kvistgaard/Danmark

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E-Mail: chembo@chembo.dk
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