# US 8,784,576 B2 · Carburizing in hydrocarbon gas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,784,576 B2 - Document ID: US8784576B2 - Status: Granted - Kind: B2 - Application number: 11/922,773 - Filed: 2006-06-21 - Published: 2009-07-16 - Granted: 2014-07-22 - Earliest claimed: 2005-06-22 - Assignees: Bodycote Netherlands Holding BV - Applicants: Marcel Somers; Thomas Christiansen - Inventors: Marcel Somers; Thomas Christiansen - Web page: https://patentgrep.com/patent/US8784576B2 ## CPC - C23C 8/20: Carburising - C23C 8/06: using gases (C23C8/36 takes precedence) - C23C 8/30: Carbo-nitriding - 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 (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) ## Abstract The invention relates to a method of gas carburizing a metallic article, where at least the surface region of the article consists of an alloy with a chromium content of at least 10 wt %. The carburizing is carried out by means of a gas containing carbon, which gas is heated to a temperature below approximately 5500C. The gas is an un-saturated hydrocarbon gas. ## Claims ### Claim 1 A method of gas carburizing an article, where at least a surface region of the article comprises an alloy with a chromium content of at least 10 wt %, wherein the article is carburized with a gas for activation of the surface and as a source of carbon for diffusion into the surface, wherein the gas is heated to a temperature below 550° C., and wherein the gas comprises a halogenated unsaturated hydrocarbon gas. ### Claim 2 (depends on 1) The method according to claim 1, wherein the gas further comprises a halogenated hydrocarbon gas in addition to the halogenated unsaturated hydrocarbon gas. ### Claim 3 (depends on 1) The method according to claim 1, wherein the hydrocarbon gas at least partly contains acetylene (C2H2). ### Claim 4 (depends on 1) The method according to claim 1, wherein the hydrocarbon gas is diluted with H2. ### Claim 5 (depends on 1) The method according to claim 1, wherein the hydrocarbon gas is mixed with a nitrogen-containing gas, and where the temperature is kept below 450° C. ### Claim 6 (depends on 5) The method according to claim 5, wherein the nitrogen containing gas is NH3. ### Claim 7 (depends on 1) The method according to claim 1, where at least the surface region of the article is an iron or nickel base alloy. ### Claim 8 (depends on 7) The method according to claim 7, wherein at least the surface region of the article is made of a ferritic, an austenitic, a martensitic, or a duplex stainless steel. ### Claim 9 (depends on 7) The method according to claim 7, wherein at least the surface region of the article is made of a nickel based alloy. ### Claim 10 (depends on 1) The method according to claim 1, wherein at least the surface region of the article is made of sintered powder metal. ### Claim 11 (depends on 1) The method of claim 1, wherein the carburizing is carried out at atmospheric pressure. ### Claim 12 (depends on 1) The method according to claim 1, wherein the carburizing is carried out at sub-atmospheric pressure. ### Claim 13 (depends on 1) The method according to claim 1, wherein the carburizing is carried out in a fluidized bed furnace. ### Claim 14 (depends on 1) The method according to claim 1, wherein the hydrogen atom of at least a part of the hydrocarbon gas is substituted with fluoride (F), chloride (CI), bromide (Br) or iodide (I). ### Claim 15 (depends on 1) The method according to claim 1, wherein the hydrocarbon gas comprises acetylene (C2H2), propane (C3H3) or a mixture thereof. ### Claim 16 (depends on 1) The method according to claim 1, wherein the surface layer is carburized in hydrocarbon gas at a temperature above 350° C. and below 510° C. ### Claim 17 (depends on 1) The method according to claim 1, wherein the surface layer is carburized in hydrocarbon gas at a temperature below 510° C. ### Claim 18 A method of gas carburizing an article, where at least a surface region of the article comprises an alloy with a chromium content of at least 10 wt %, wherein the article is carburized with a gas for activation of the surface and as a source of carbon for diffusion into the surface, wherein the gas is heated to a temperature below 550° C., wherein the gas comprises an unsaturated hydrocarbon gas, and wherein at least the surface region of the article is made of sintered powder metal. ### Claim 19 A method of gas carburizing an article, where at least a surface region of the article comprises an alloy with a chromium content of at least 10 wt %, wherein the article is carburized with a gas for activation of the surface and as a source of carbon for diffusion into the surface, wherein the gas is heated to a temperature below 550° C., wherein the gas comprises an unsaturated hydrocarbon gas, and wherein the carburizing is carried out in fluidized bed furnace.