METHOD FOR MODIFYING SURFACE OF PISTON FOR INTERNAL COMBUSTION ENGINE, AND PISTON FOR INTERNAL COMBUSTION ENGINE

摘要

There is provided a piston with a surface modified layer for an internal-combustion engine by a method using a particle to be ejected made of iron-based alloy having a diameter of 20 to 200 μm, a thermal conductivity of 30 W/m·k or less at 25° C., and a specific gravity of 7.5 g/cm3 or greater. The method includes: first treatment for ejecting the particle onto a surface of a piston made of aluminum-silicon alloy or aluminum-copper-based alloy in a space in which oxygen exists at arc height value of 0.07 to 0.13 mm (N), second treatment for ejecting the particle onto the surface of the piston in a space in which oxygen exists at arc height of 0.13 to 0.22 mm (N), and heating treatment applying to the piston for 1.5 hours or longer at 170 to 190° C. in a space in which oxygen exists.

主权项

1. A method for modifying a surface of a piston for an internal-combustion engine by using a shot made of an iron-based alloy as a particle to be ejected having a diameter of 20 μm to 200 μm, a thermal conductivity of 30 W/m·k or less at a temperature of 25° C., and a specific gravity of 7.5 g/cm3 or greater, comprising:
a first ejection treatment for ejecting the particle to be ejected onto a surface of a piston in a space in which oxygen exists under conditions such that an arc height value is set within a range from 0.07 mm (N) to 0.13 mm (N), and the piston being made of an aluminum-silicon alloy or an aluminum-copper-based alloy and obtained by casting and forging; a second ejection treatment for ejecting the particle to be ejected onto the surface of the piston to which the first ejection treatment has been applied in a space in which oxygen exists and under conditions such that an arc height value is set within a range from 0.13 mm (N) to 0.22 mm (N); and a heating treatment subsequently applying to the piston for 1.5 hours or longer at a temperature of 170° C. to 190° C. in a space in which oxygen exists.