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Plasma coating of engine block cylinder bores

The solution is based on an optimum material selection between the piston rings and cylinder bores. In a continuous process, the engine blocks are grit blasted, cleaned and plasma sprayed. The plasma sprayed coatings are thin (140-200 microns), uniform (± 10% of the nominal coating thickness) and smooth (Ra = 8-12 microns). The system is designed for a prototype series and can spray up to 200 inline four-cylinder engine blocks per day. 

The plasma coating of the cylinder bores is able to replace the pressing, shrinking, casting-in of cylinder sleeves or the use of expensive, nickel containing galvanic plating processes. By replacing sleeves the wall thickness between the individual bores of the engine blocks can be made much thinner. This results in a more compact construction, considerable weight savings and lower production costs of engine blocks.

The potential for lower friction values (compared to cast iron) and for excellent wear properties of the plasma coating result in the required life time of the engine blocks.

In some cases the plasma coating is able to replace a galvanic process, which results in an environmentaly friendly solution because nickel based materials are no longer being used.

Depending on the coating, finishing costs of the plasma sprayed coating may be lower because the coating can be honed faster, and with less wear to the honing tools.

In cooperation with the customer, a molybdenum-based material was developed and supplied by Sulzer Metco which fulfils the requested friction behaviour and wear properties. This results in a coating solution meeting the economics and performance goals.

For more information please email contactus@twi.co.uk

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