# US 2019/0376173 A1 · Chemical activation of self-passivating metals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0376173 A1 - Document ID: US20190376173A1 - Status: Published application - Kind: A1 - Application number: 16/433,083 - Filed: 2019-06-06 - Published: 2019-12-12 - Earliest claimed: 2018-06-11 - Assignees: Swagelok Company - Applicants: Swagelok Company - Inventors: Cyprian A.W. Illing; Peter C. Williams; Christina Semkow - Web page: https://patentgrep.com/patent/US20190376173A1 ## CPC - C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence) - C23C 8/22: of ferrous surfaces - C23C 8/26: of ferrous surfaces - C23C 8/30: Carbo-nitriding - C23C 8/32: of ferrous surfaces - C23C 8/80: After-treatment - C21D 1/06: Surface hardening - 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) - 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 (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B) ## Abstract A workpiece made from a self-passivating metal and having one or more surface regions defining a Beilby layer as a result of a previous metal shaping operation is activated for subsequent low temperature gas hardening by exposing the workpiece to the vapors produced by heating a non-polymeric N/C/H compound. ## Claims ### Claim 1 A process for depassivating a metal workpiece made from a self-passivating metal, the workpiece having one or more surface regions which define a Beilby layer, the process comprising exposing the workpiece to contact with vapors produced by heating a non-polymeric N/C/H compound to a processing temperature which is high enough to convert the non-polymeric N/C/H compound to vapors, wherein the non-polymeric N/C/H compound (a) contains at least one carbon atom, (b) contains at least one nitrogen atom, (c) contains only carbon, nitrogen, hydrogen and optionally halogen atoms, (d) is solid or liquid at 25° C. and atmospheric pressure, and (e) has a molecular weight of ≤5,000 Daltons, and further wherein the processing temperature is below a temperature at which nitride and/or carbide precipitates form. ### Claim 2 (depends on 1) The process of claim 1, wherein the processing temperature is ≤500° C. ### Claim 3 (depends on 2) The process of claim 2, wherein the processing temperature is ≤475° C. ### Claim 4 (depends on 1) The process of claim 1, wherein the non-polymeric N/C/H compound has a molecular weight of ≤500 Daltons. ### Claim 5 (depends on 4) The process of claim 4, wherein the non-polymeric N/C/H compound contains 5-50 C+N atoms. ### Claim 6 (depends on 5) The process of claim 5, wherein the non-polymeric N/C/H compound contains 6-30 C+N atoms, alternating C═N bonds and one or more primary amine groups. ### Claim 7 (depends on 1) The process of claim 1, wherein the non-polymeric N/C/H compound is an aromatic amine containing 6-30 C+N atoms. ### Claim 8 (depends on 1) The process of claim 1, wherein the non-polymeric N/C/H compound is unsubstituted in the sense of containing only C, N and H atoms. ### Claim 9 (depends on 1) The process of claim 1, wherein at least some of the non-polymeric N/C/H compound is substituted with one or more halogen atoms. ### Claim 10 (depends on 9) The process of claim 9, wherein the amount of halogen-substituted non-polymeric N/C/H compound used is ≥5 wt. % of the total amount of non-polymeric N/C/H compound used. ### Claim 11 (depends on 10) The process of claim 10, wherein the amount of halogen-substituted non-polymeric N/C/H compound used is ≤30 wt. % of the total amount of non-polymeric N/C/H compound used. ### Claim 12 (depends on 1) The process of claim 1, wherein the self-passivating metal is a titanium-based alloy or an iron-based, nickel-based, cobalt based or manganese-based alloy which contains at least 10 wt. % Cr. ### Claim 13 The process of clam 12, wherein the self-passivating metal is a titanium-based alloy. ### Claim 14 The process of clam 12, wherein the self-passivating metal is an iron-based, nickel-based, cobalt based or manganese-based alloys which contains at least 10 wt. % Cr. ### Claim 15 The process of clam 14, wherein the self-passivating metal is a stainless steel containing 10 to 40 wt. % Ni and 10 to 35 wt. % Cr. ### Claim 16 (depends on 1) The process of claim 1, wherein the self-passivating metal is a titanium-based alloy or an iron-based, nickel-based, cobalt based or manganese-based alloy which contains at least 10 wt. % Cr, the process further comprising subjecting the workpiece to an augmented low temperature gas hardening process selected from the group consisting of low temperature carburization, low temperature nitriding and low temperature carbonitriding, thereby forming a hardened surface layer on the workpiece surfaces without formation of nitride or carbide precipitates, said augmented low temperature gas hardening process being carried out by contacting the workpiece with an additional gas different from said vapors, said additional gas containing at least one of a compound capable of decomposing to yield nitrogen atoms for nitriding, a compound capable of decomposing to yield carbon atoms for carburization, and a compound capable of decomposing to yield both nitrogen atoms and carbon atoms for carbonitriding. ### Claim 17 (depends on 16) The process of claim 16, wherein the workpiece is contacted with the additional gas only after the workpiece has been depassivated. ### Claim 18 (depends on 16) The process of claim 16, further comprising exposing the workpiece to atmospheric oxygen after the workpiece has been depassivated, and further wherein the depassivated workpiece is free of fluorine atoms. ### Claim 19 (depends on 18) The process of claim 18, wherein depassivation of the workpiece is carried out in a depassivation furnace, wherein low temperature gas hardening is accomplished in a thermal processing furnace which is different from the depassivation furnace, and wherein the workpiece is exposed to atmospheric oxygen while being transferred between the depassivation furnace and the thermal processing furnace. ### Claim 20 A process for simultaneously depassivating and surface hardening a workpiece without formation of nitride or carbide precipitates, the workpiece being made from a corrosion-resistant, self-passivating metal comprising a stainless steel containing 5-50 wt. % Ni and at least 10 wt. % Cr, a nickel-based or manganese-based alloy containing at least 10 wt. % Cr or a titanium-based alloy, the workpiece having one or more surface regions which define a Beilby layer as a result of a previous metal shaping operation, the surfaces of the workpiece also having a coherent protective coating formed either from chromium oxide or titanium oxide, the process comprising contacting the workpiece with vapors produced by heating a non-polymeric N/C/H compound to a processing temperature which is high enough to convert the non-polymeric N/C/H compound to vapors, wherein the non-polymeric N/C/H compound (a) contains at least one carbon atom, (b) contains at least one nitrogen atom, (c) contains only carbon, nitrogen, hydrogen and optionally halogen atoms, (d) is solid or liquid at 25° C. and atmospheric pressure, and (e) has a molecular weight of ≤5,000 Daltons, wherein the processing temperature is less than 500° C. and also below a temperature at which nitride and/or carbide precipitates form thereby depassivating the workpiece by making its coherent protective coating transparent to the passage of nitrogen and carbon atoms and simultaneously surface hardening the workpiece by causing carbon and/or nitrogen atoms to diffuse into the surface of the workpiece without formation of the type of carbide and/or nitride precipitates which cause the corrosion resistance of the self-passivating metal to be lost.