Provided is a metal component having a surface layer that is resistant to heat/corrosion and wear, the surface layer having high durability with respect to repeated thermal stress. The present invention comprises a parent material that is an iron-based metal or a nickel-based metal, and a surface improvement layer formed on the surface of the parent material. The surface improvement layer is configured so as to include a chromium compound layer that is present on the surface side, and a deposition layer that is present between the chromium compound layer and the parent material, the deposition layer being such that the chromium compound is deposited in a parent-material metal constituting the parent material. The thermal expansion coefficients of these layers increases sequentially from the surface toward a deep section such that the thermal expansion coefficient of the chromium compound layer is less than that of the deposition layer, which in turn is less than that of the parent material. Specifically, the difference in thermal expansion coefficient between each of the layers is low. This makes it possible to raise the durability of the surface layer with respect to repeated thermal stress and to maintain the characteristics of heat/corrosion resistance and wear resistance of the surface layer. There are many environments and applications in which the present invention can be used.
C23C 28/00 - Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of main groups , or by combinations of methods provided for in subclasses and
Provide a metal surface reforming method enabling metallic products with superior characteristics such as surface hardness, heat resistance, corrosion resistance, high temperature oxidation, high temperature corrosion, and environmental corrosion and the like.
Halogenation treatment of heating and retaining a base material in an atmosphere containing a halogen based gas is performed on a base material of iron based metal or nickel based metal, then nitride processing of heating and retaining the halogenated base material described above in an atmosphere containing a nitrogen source gas is performed, then chromizing treatment is performed by placing the nitrided base material in a powder containing metal chromium powder to form a surface reformed layer on the base material described above. These metallic products obtained have high hardness, superior heat resistance and corrosion resistance, and exhibit superior performance in high temperature oxidation, high temperature corrosion, erosion, and cavitation and the like environments. Further, the metallic products described above exhibit superior performance in acid or alkali environments, neutral environments, and corrosive environments such as chlorides like salt water.
C22F 1/10 - Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
C23C 12/00 - Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material surfaces
C23C 8/02 - Pretreatment of the material to be coated
C23C 8/08 - Solid state diffusion of only non-metal elements into metallic material surfacesChemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
C23C 10/02 - Pretreatment of the material to be coated
C23C 10/28 - Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
C23C 10/30 - Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes using a layer of powder or paste on the surface
C23C 28/00 - Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of main groups , or by combinations of methods provided for in subclasses and
C22F 1/00 - Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
3.
METHOD FOR ALTERING SURFACE OF METAL, AND METALLIC PRODUCT
A method for altering the surface of a metal is provided with which it is possible to obtain a metallic product excellent in terms of surface hardness, heat resistance, corrosion resistance, resistances to high-temperature oxidation, high-temperature corrosion, and environmental corrosion, and other property. A base that is an iron-based metal or nickel-based metal is subjected to a halogenation treatment in which the base is heated and held in an atmosphere comprising a halogen-based gas, subsequently to a nitriding treatment in which the halogenated base is heated and held in an atmosphere comprising a nitriding gas, and then to a chromizing treatment in which the nitrided base is heated and held in a powder comprising a chromium metal powder, thereby forming a surface alteration layer in the base material. The metallic product obtained shows extremely high hardness, is excellent in terms of heat resistance and corrosion resistance, and exhibits excellent performance in environments which may cause high-temperature oxidation, high-temperature corrosion, erosion, cavitation, etc. The metallic product exhibits excellent performance even in acidic or alkaline environments, neutral environments, and corrosive environments including chlorides, such as seawater.
C23C 12/00 - Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material surfaces
C22F 1/00 - Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
C22F 1/10 - Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
patents
