Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
  • C21D3/02—Extraction of non-metals
  • C21D3/04—Decarburising
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/06—Metallic material
  • C23C4/08—Metallic material containing only metal elements
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/18—After-treatment

Definitions

• the present invention relates to a method of forming an oxidation-resistant coating on a steel substrate, such as steel sheet or wire, this coating comprising an oxidation-resistant material consisting of one or more of the metals Cr, Ni, Co, M0, or an alloy of two or more of these metals with one another or an alloy of one or more of these metals with iron or with other elements, the coating being formed by depositing the oxidationresistant material on the steel substrate (eg. by metalization or powder compacting techniques) and then subjecting the coated substrate to heat treatment to cause diffusion of the constituents of the substrate and coating.
• oxidation-resistant coatings are in the protection of ferrous products from corrosion and oxidation, and to this end it has already been suggested to employ powders comprising one or more of the metals Cr, Ni, Co and M or their alloys, whose protective properties are well known. With steel substrates it has in the past been found that satisfactory results, as far as corrosion resistance in an aqueous medium is concerned, could be obtained in practice with titanium-stabilized steels only.
• Methods used at present include carefully cleaning the substrate, then depositing an alloy on the substrate by spray metallization or by spreading and compacting of powder, and finally heat treating the coated substrate at a high temperature in a dry hydrogen atmosphere in order to cause diffusion of the alloy, deoxidation of the coating, and also decarburization of the substrate and the coating. After this, the coated product can be rolled and recrystallization annealing can take place depending upon the mechanical and structural properties desired in the final product.
• What is desired is a method of forming an oxidationresistant coating which does not undergo corrosion in an aqueous medium even when the substrate consists of ordinary steel, such as rimming steel or aluminum killed steel, whose carbon content is at least about 0.050 percent (by weight), this carbon being free.”
• the heat treatment comprises the following three stages in sequcnce:
• a decarburization stage in a decarburizing atmosphere such as carbon dioxide atmosphere or a wet hydrogen atmosphere
• the method is thus characterized in that diffusion takes place in an active atmosphere whose composition varies in the course of time.
• the temperature may also vary from stage to stage.
• the three stages of the heat treatment concerned can be carried out during a single annealing cycle.
• the preliminary diffusion stage is intended to ensure adhesion of the coating to the substrate and simultaneous removal of the oxygen present in the coating, and a dry hydrogen atmosphere is necessary in order to avoid oxidation of the interface between substrate and coating either due to the presence of this oxygen (the oxygen is eliminated as H O) or due to the action of that oxygen which would be brought about by an active gas whose dew point is not sufficiently low. Such oxidation of the interface would adversely affect diffusion and would inhibit adhesion of the coating.
• the decarburization stage is preferably carried out under a wet hydrogen atmosphere for well-known reasons of efficiency.
• the final diffusion stage is designed to complete the diffusion of the constituents of the coating and to prevent excessive oxidation of the surface of the substrate as a consequence of the preceding stage carried out in a wet hydrogen atmosphere.
• the preliminary diffusion stage at a temperature of 700C to l300C (preferably l000C to l250C) for 16 hours to A hour;
• the decarburization stage at a temperature of 900C to l300C for 4 hours to A hour according to the thickness of the coated substrate;
• the coating material may be deposited as a powder of one or more of the metals Cr, Ni, Co M0, or alloys of these metals, preferably an iron alloy of Cr or of Ni- Cr.
• the carbon contentof the powder will be between 0.020 and 1 percent.
• the deposition of the coating material is advantageously carried out either by metalization by means of a flame torch or an arc torch, or by a distribution or spreading operation followed by a compacting operation.
• the present invention particularly aims to a product whose coating advantageously has a carbon content lower than 0.020 percent.
• the coated substrate obtained may The above-described method enables a coating to be obtained whose microstructure is free from any intergranularcarbide, this ensuring good corrosion resistance in an aqueous medium.
• the coating obtained provides an improvement (with respect to other processes) in the surface finish after rolling and recrystallization.
• a heat treatment consisting of diffusion for 16 hours at 1 150C in dry hydrogen leads to the formation of a coating having a carbon content between 0.150 percent and 0.200 percent by weight.
• a method of producing a steel product having a decarburized oxidation-resistant coating comprising the steps of depositing on a mild steel substrate a coating of at least one oxidation-resistant material selected from the group consisting of the metals Cr, Ni, Co, and Mo, alloys of at least two of these metals with each other, and alloys of at least one of these metals with iron or other elements; and then subjecting the coated substrate to heat treatment to cause diffusion of constituents of the substrate and coating, the heat treatment comprising the following three stages in sequence;
• a method as claimed in claim-4 in which a powder of an iron-alloy of nickel and chromium is deposited on the substrate.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Coating By Spraying Or Casting (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=3860707

Family Applications (1)

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Cited By (5)

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Citations (5)

Family Cites Families (3)

• 0
  • BE BE794757D patent/BE794757A/xx unknown
• 1974
  • 1974-01-18 IT IT67140/74A patent/IT1009109B/it active
  • 1974-01-21 NL NL7400779A patent/NL7400779A/xx not_active Application Discontinuation
  • 1974-01-24 SE SE7400936A patent/SE390033B/xx unknown
  • 1974-01-28 CA CA191,023A patent/CA1011226A/en not_active Expired
  • 1974-01-29 LU LU69266A patent/LU69266A1/xx unknown
  • 1974-01-29 JP JP49012127A patent/JPS49106444A/ja active Pending
  • 1974-01-30 GB GB423874A patent/GB1408127A/en not_active Expired
  • 1974-01-30 FR FR7403710A patent/FR2215489B1/fr not_active Expired
  • 1974-01-30 US US437916A patent/US3868277A/en not_active Expired - Lifetime

Patent Citations (5)

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