Method for surface treatment of a skirt portion of a piston for an internal combustion engine and a piston for an internal combustion engine

Abstract

A piston allowing a lubrication layer of a resin coating with a low friction coefficient to be tightly adhered to a skirt portion of a piston for an internal combustion engine, with low friction, superior wear resistance, and superior anti-seizing properties and that can reduce wear of a cylinder inner wall even if the lubrication layer is peeled off or abraded, is provided. Metal or ceramic fine particles having an average particle diameter of 20 μm to 400 μm are injected with compressed air or compressed nitrogen as a mixture fluid onto the skirt portion of the piston, made of an aluminum alloy and produced by a method such as casting or forging, at an injection speed of 80 m/s or more or an injection pressure of 0.2 MPa or more to be collided with the skirt portion, thereby uniformly making a microstructure of a piston base material fine-grained in a depth range of 1 μm to 15 μm from a surface of the skirt portion and forming a modified layer with an activated surface. A lubrication layer is formed on the modified layer, for example, by applying a resin with a low friction coefficient, while a surface of the modified layer is being activated.