NIKASIL, what it is, why it is used and when it should be renewed?
See below our explanations to questions briefly.
What is it – NIKASIL plating (coating)?
A technical translation – it is a Nickel and Silicon Carbide composite (NiSC). Before it is plated on the aluminum surface of the cylinder, it can be characterized as a liquid Nickel and Silicon Carbide powder composite. This composite is electrolytically codeposited in a very thin layer to the aluminum cylinder surface, making a very hard plating. A good example for the structure is a comparison with concrete – the nickel is the cement, which holds together the stone, in this case – the silicon carbide.
High hardness is only one of very important features, that is necessary for the effective cylinder and piston group work, which is provided by NiSC coating.
High hardness is only one of very important features, that is necessary for the effective cylinder and piston group work, which is provided by NiSC coating.
Why is it used in a contemporary aluminum cylinders coating?
There must be mentioned two important aluminum features, because of what it is used as a base for the engine cylinder and other parts. That is weight and high heat conduction. However it is not enough wear resistant, in other words – it is too soft. Aluminum is too soft for contact with piston rings and piston, therefore the friction with them would cause the cylinder wearing off. Therefore it is coated with NiSC layer, that allows the aluminum cylinder to maintain not only its important weight and heat transfer features, NiSC is also an oil holding composite.
Little about each NiSC coating advantage.
1. Hardness – NiSC hardness is close to diamond hardness because of Silicon Carbid particles. The hardness is so high, that during the processing of cylinder (honing), which is done after the NiSC plating, is done by special diamond abrasives. This process is necessary to get the cylinder’s diameter size up to thousands of a millimeter thick. After the honing a wavy scratch is seen, that is also necessary the cylinder lubricate properly.
2. Oil resistance – NiSC coating is oil holding one because of the silicon carbide particles. It means that there is an oil layer between the cylinder wall and the moving piston with rings. This layer not only reduces the friction, because of oil features, but also works as isolation for inflammable mixture and waste gasses flowing away along the compression rings. It means that there is a higher pressure in the cylinder, which is on base of the engine work and energy. No density can be a reason for high fuel consumption, as well as snatch engine work, hard motorcycle starting and other engine work disadvantage.
3. Heat transfer to the cooling system - NiSC coating is also a good heat transferee, which means, the heating created within pressure and burning processes easy reaches aluminum, which already fills and also transfers heat to the cooling system. The engine working temperature is very important, that the engine could work at maximum efficiency, and parts, as well as oil, would not be dependent under the heating over, that can cause wrong engine work and even kill it.
What are the main reasons for NiSC wear?!
The reasons of NiSC coating damage – worn rings or their seats shredded trace in the piston, mechanical damages (broken valves, etc.), sand and other abrasives entered through the air filter, old and dirty oil, wrong size pistons, an overheated engine. These are main reasons, which can cause NiSC damage. To escape it, it is needed to follow the definite working hours of parts and factors, they can influence, e.g., defect of air filter.
When the NIKASIL (NiSC) coating needs be re-plated?!
If you change rings and pistons in time, drive with good motor oils and change them in time, carefully follow up the condition of air filters, thus preventing abrasives getting in the cylinder, then it is not needed to change the NiSC coating! Mostly defects (damages) arise from „driven over” rings and pistons. Worn out pistons group defect usually appears on the top of cylinder, where the rings change their movement direction downward. Firstly that appears as socket, felt by running with a finger along the upper edge of cylinder wall. In case such defect is lingering, you can see a light line denoting that NiSC coating is „ate” up to aluminum with the ring edges. Driving a motorcycle with such cylinder necessarily will cause the energy loss, a shorter working time of new rings and higher NiSC re-plating costs.
Available cylinder's list PDF
Exchange cylinder's list PDF (refreshed on 31.05.2010)
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