The piston ring is a metal seal, which passes the high temperature generated by combustion to the cylinder and the cooling water. The peak temperature of the first ring is maintained at an average of 315℃ and it performs the most important sealing function under the influence of the highest air pressure. The second and third ring bear less pressure. The oil ring strip off the remaining oil on the surface and keep a thin layer of lubrication on the surface. Therefore, it prevents excess oil from entering and burning in the combustion chamber. Piston rings can have different shape characteristics, as well as coating properties. The coating properties of the ring are very important in terms of wear and heat transfer performance.
CONSTRUCTION TYPE OF PISTONR RING
Piston rings come in different types and coatings, depending on their use and function.
COMPRESSION RINGS
The compression rings are the most basic parts used to generate pressure and seal during combustion.
OIL RINGS
The oil ring is specially designed for oil control. It provides lubrication between the piston and the bushing during circulation. Multiple oil rings may also be used, according to the piston design.
PISTON RING SURFACE TREATMENT
RING COATING : Rings made of cast iron or steel materials cannot be used immediately after production, because the harsh working conditions and the corrosion caused by the natural structure of the material result in serious problems in terms of product life. To overcome these problems and extend the life of the piston ring, the piston surface is applied with many types of coatings.The most common type of coating is chrome. However, under these harsh conditions, chrome plating is not enough. With the development of technology, more efficient coating PVD and DLC are applied. These coating types are becoming increasingly common due to their high heat and wear resistance and longer service life.
RING COATING AND SURFACE TREATMENT : Cr = Chrome-plated,Mo = Molybdenum-coated,P = phosphating,Ox = Oxidation-coatd,Sn = Tin-coated,CCC= Chromium-Ceramics Coating,PVD = Chromium Nitride ,CDC = Chrome Diamond Coating ,DLC = Diamond-Like Coating
Molybdenum-coated : The circumference of the ring is covered with molybdenum to prevent wear. To avoid burn marks, the working surface of the ring can be filled or covered with molybdenum. Coating can be done by flame spray and plasma spray. The high melting point of molybdenum and porous structure facilitates lubrication, making the piston ring more durable. It has high thermal conductivity and wear resistance.
Chromium-Ceramics : Chromium ceramic coating (CCC) is a composite coating type obtained from a network structure formed by chromium and alumina elements. These coatings are mainly used for the first ring of diesel engine piston.Difference between CCC coating and hard chromium coating.Better wear resistance,Higher melting point,Higher hardness and crack density,Because of these advantages, CCC coatings are used to extend engine life and create low emissions in vehicles.
Chromium Nitride : The method formed by the deposition of a hard coating on the ring surface by the gas phase is called the PVD method. This method provides evaporation and ionization of metals by electric arc or ion bombardment. The separated and regulated metal ions are pushed onto the surface of the assembly. As a result, the metal atoms react with reactive gases to form nitrites, carbides and oxides. After the reaction, a thin coating is formed on the ring working surface. It shows high wear resistance due to the ceramic properties of the coating.
Chrome Diamond Coating : This coating type is used in the first ring of diesel engines. It can be applied to flexible and alloy cast iron, carbon steel. Diamond particles are used instead of ceramic particles.
Diamond-Like Coating : Friction is reduced and wear resistance is increased for this coating. DLC coatings are environmentally friendly due to their properties. It has strong chemical bonds that it does not break under mechanical tension. They're not crystallized. They're amorphous. This material is a very strong material due to its structure. It is more resistant to friction than other coatings.
