Patent ID: 8231741

Claim:
An internal combustion piston comprising a modified layer produced by a surface treatment including: injecting injection powders having a diameter of 20 μm to 400 μm and containing a reinforcing element to be collided with a surface of said internal combustion piston obtained by casting and forging by injecting at an injection speed of 80 m/s or more or at an injection pressure of 0.3 MPa or more, said reinforcing element improving a strength of an alloy comprising said piston when being diffused and penetrated in said alloy, wherein by said surface treatment, oxides generated on said surface of said piston by said casting and forging are removed, and surface flaws generated on said surface are repaired, whereby said modified layer is formed to have a uniformly fine-grained metal microstructure which contains said reinforcing element in said injection powders diffused and penetrated in the vicinity of said surface of said piston and an alloy element of said alloy comprising said piston, and as said reinforcing element contained in said injection powders reinforcing the strength of said alloy, Fe is a primary element, and said modified layer comprises 1 mass % to 10 mass % of Fe, 11 mass % to 25 mass % of Si, and 0.1 mass % to 10 mass % of N, and the rest thereof being Al.