Development of Piston Surface Treatment for Internal Combustion Engine

Low-friction surface treatment technology and machined piston surface that provided high wear resistance was developed for the piston skirt of an internal combustion engine. Conventional low-friction coating materials consist of a solid lubricant, such as molybdenum, and low friction were realized by self-lubrication, wear and abrasion; therefore it was not possible to expect the effectiveness of performance to be maintained. The newly developed technology uses a high-strength film which has an oil adsorption effect, enabling friction to be reduced by about 40% while improving wear resistance about 5-fold compared to conventional coating materials. Conventional piston surface have a streak in wave shape for oil maintenance. The top of the streak has sharp edges causing an increase of partial aspect pressure, long term of break-in run and early coating abrasion. Developed piston surface for coating has the suitable trapezoid shape that causes low-friction and high wear resistance. The newly developed surface treatment and machining technology improves 30% of wear resistance and 4% of maximum engine output. Since this technology employs piston spray coating technology and processing techniques, the new film can be applied by simply replacing the material and the machined tool without any need for special production equipment.