Surface treatment method of metal products and metal products

Abstract

The invention provides a surface treatment method, which can continuously form a uniform nanocrystalline structure along the surface for hard or soft metal products. Spray roughly spherical spray particles with a median diameter of 1 to 20 μm and a fall time in air of 10 seconds / m or more on metal products at a spray pressure of 0.05 MPa to 0.5 MPa particles. Thereby, even a metal product made of a soft material does not produce a lamellar processed structure, and a nanocrystalline structure layer can be continuously and uniformly formed along the surface of the metal product within a predetermined depth from the surface. The average crystal grain size of the nanocrystals in the nanocrystalline structure layer is miniaturized to 300nm or less, preferably 100nm or less, and can impart high compressive residual stress in the range of about -180MPa to maximum -1200MPa, and can realize surface strengthening of metal products.

Description

technical field [0001] The present invention relates to a method for surface treatment of metal products and the metal products surface treated by said method, and more specifically relates to making the crystal structure near the surface of the metal product nano A surface treatment method for strengthening the surface of a metal product and a metal product whose surface has been strengthened by said method. Background technique [0002] It is known that the strength of metal materials increases in proportion to the reciprocal of the square root of the crystal grain size, satisfying the Hall-Petch relationship, and the miniaturization of the crystal grain size that brings such an effect is also used in metals. Surface strengthening of products. [0003] In particular, it has been reported that in metal products in which the crystal grain size near the surface is miniaturized to the nanometer level, not only the surface hardness is sharply increased, but also the wear resis...

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Problems solved by technology

[0005] In addition, the formation mechanism of the nanocrystalline structure of shot peening is still not very clear, but it is described in Patent Document 1 and Non-Patent Document 1 described later that the SS400 steel (HV1.20GPa (HV122) as a soft material ) is an example of surface treatment of high-speed steel (SKH59) made of shot blasting with an average particle size of 45 μm at 0.5 MPa for 30 seconds, using the same conditions on SCr420 carburized and quenched steel as a hard material (initial hardness HV7.55GPa (HV770) ) is an example of surface treatment by shot blasting, and it is described that there is a large difference in the structure of the nanocrystalline structure formed in the two examples (Patent Document 1, Non-Patent Document 1)

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