Patent ID: 7767033
Filing Date: 2010-08-03
Classification: F02F,Y10T

Abstract:
1. A method for surface treatment of an internal combustion piston made from casting and forging of an aluminum-silicon alloy comprising: providing injection powders having a diameter of 20 μm to 400 μm and containing a reinforcing element, diffusing and penetrating the reinforcing element on a surface of the internal combustion piston by injecting the injection powders to collide with the surface of the internal combustion piston at an injection speed of 80 m/s or more or at an injection pressure of 0.3 MPa or more, whereby oxides of surface flaw portions generated on said piston surface by said casting and forging are removed, said surface flaw portions generated on said surface are repaired, an alloy element in said alloy of said piston is fine-grained in vicinity of said surface of said piston, and whereby a modified layer having a uniformly fine-grained metal microstructure which contains said alloy element and said reinforcing element is formed on said piston surface; wherein an element exhibiting a photocatalytic function by oxidation is selected as said reinforcing element, and said modified layer is formed on a top surface of said piston, in which said reinforcing element is oxidized so that bonding with oxygen is decreased from a surface of said modified layer to an inside of said modified layer; and said injection powders containing said reinforcing element further include a noble metal element, and said noble metal element is supported in said modified layer.