| 摘要 |
PROBLEM TO BE SOLVED: To form a surface layer, harder than that obtained by ordinary surface hardening, in a short time by irradiating the surface of a coating film with laser beam to melt the coating film and the surface part of the material to be treated and then applying rapid cooling. SOLUTION: As a ferrous metal to be treated, carbon steel, cast iron, cast steel, or alloy steel such as stainless steel is used. For example, a carbon- containing coating agent 2 is applied to the surface of a carbon steel 1 to form a coating film 3, and the coating film 3 and the surface part of the carbon steel 1 are melted by irradiating the surface 4 of the coating film 3 with laser beam 4, followed by rapid cooling. At this time, carbon in the coating agent is allowed to penetrate into the surface part of the material to be treated (carbon steel) and then rapid cooling is carried out, by which a surface layer of martensitic structure containing cementite structure is formed. The coating agent is a coating material prepared by mixing carbonaceous material, binder, surfactant, and water, and its thickness is about 20μm. By this method, sufficient surface hardness can be obtained independently of the quality of the base material. |
