# US 9,433,897 B2 · Process for producing a diffusion barrier layer and process for producing an exhaust gas treatment unit

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- Number: US 9,433,897 B2
- Document ID: US9433897B2
- Status: Granted
- Kind: B2
- Application number: 14/291,133
- Filed: 2014-05-30
- Published: 2014-09-18
- Granted: 2016-09-06
- Earliest claimed: 2011-11-30
- Assignees: EMITEC Gesellschaft fuer Emissionstechnologie mbH
- Applicants: Emitec Gesellschaft Fuer Emissionstechnologie Mbh
- Inventors: Dieter Lutz
- Web page: https://patentgrep.com/patent/US9433897B2

## CPC

- B01D 53/92: of engine exhaust gases (exhaust {or silencing} apparatus {for internal combustion engines, machines or engines in general}, having means for purifying, {rendering innocuous} or otherwise treating exhaust gases F01N3/00)
- B01D 46/2422: {Mounting of the body within a housing}
- B01J 23/75: Cobalt
- B01J 23/755: Nickel
- B01J 37/0238: {via the gaseous phase-sublimation}
- C21D 8/04: to produce plates or strips for drawing, e.g. for deep-drawing
- C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence)
- C23C 8/10: Oxidising
- C23C 8/14: Oxidising of ferrous surfaces
- C23C 10/02: Pretreatment of the material to be coated (C23C10/04 takes precedence)
- C23C 24/08: by application of heat or pressure and heat (C23C24/04 takes precedence)
- B01J 21/04: Alumina
- F01N 3/281: {Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates}
- F01N 2370/02: used in catalytic reactors
- F01N 2450/22: by welding or brazing
- Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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)
- 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)
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## Abstract

A process for producing a diffusion barrier or blocking layer includes providing aluminum oxide on a metal sheet formed of a base material including at least iron, chromium and aluminum. A process for producing an exhaust gas treatment unit includes providing a honeycomb body and a housing in which at least one of the honeycomb body or the housing is formed of the metal sheet and the metal sheet is formed of a base material including at least iron, chromium and aluminum. The metal sheet thus includes, at least in a subregion, a surface layer including at least aluminum oxide and a metal from the group including cobalt and nickel. An exhaust gas treatment unit and a motor vehicle are also provided.

## Claims

### Claim 1

A process for producing a diffusion barrier layer including aluminum oxide on a metal sheet formed of a base material containing at least iron, chromium and aluminum, the process comprising the following steps:
a) providing the metal sheet with a surface having at least one subregion;
b) applying at least one metal oxide selected from the group consisting of cobalt oxide and nickel oxide, to the at least one subregion as a surface layer, or
applying at least one material compound able to form at least one metal oxide selected from the group consisting of cobalt oxide and nickel oxide as a result of a temperature increase, to the at least one subregion as a surface layer,
the metal oxide or the material compound in the surface layer in step b) being present in a proportion of at least 40% by weight; and
c) carrying out a heat treatment above 650° C. on the metal sheet having the surface layer causing formation of a diffusion barrier layer including aluminum oxide only in the at least one subregion of the surface layer, with reduction of the metal oxide to a metal and oxidation of aluminum diffusing out of the base material to aluminum oxide.

### Claim 2 (depends on 1)

The process according to claim 1, wherein the aluminum oxide is homogeneously distributed in the surface layer after carrying out step c).

### Claim 3 (depends on 1)

The process according to claim 1, wherein a proportion of the metal of the metal oxide or of the material compound being present in elemental form in the surface layer has increased by least 5% by weight after carrying out step c).

### Claim 4 (depends on 1)

The process according to claim 1, wherein a proportion of aluminum in the base material in step a) is in a range from 1 to 7% by weight and a proportion of aluminum in the metal oxide or in the material compound in step b) is at most 2% by weight.

### Claim 5 (depends on 4)

The process according to claim 4, wherein a proportion of aluminum in the diffusion barrier layer after carrying out step c) is at least 15% by weight.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the surface layer has a thickness of at most 1 μm [micron] after carrying out step b).

### Claim 7 (depends on 1)

The process according to claim 1, wherein the base material in step a) has a maximum of 20% of the metal of the metal oxide or the material compound from step b).

### Claim 8

A process for producing an exhaust gas treatment unit, the process comprising the following steps:
i) providing at least one metal sheet formed of a base material containing at least iron, chromium and aluminum for the formation of at least a housing or a honeycomb body from the at least one metal sheet and providing the at least one metal sheet with a surface having a subregion;
ii) applying at least one metal oxide selected from the group consisting of cobalt oxide and nickel oxide, at least to the subregion as a surface layer, or
applying at least one material compound able to form at least one metal oxide selected from the group consisting of cobalt oxide and nickel oxide as a result of a temperature increase, at least to the subregion as a surface layer;
iii) forming the honeycomb body and inserting the honeycomb body into the housing;
iv) applying brazing material at least to the honeycomb body or the housing in at least one brazing section;
v) carrying out a brazing process above 1000° C. on the at least one metal sheet including metal oxide under vacuum or protective gas, causing:
formation of a diffusion barrier layer including aluminum oxide only in the at least one subregion in the surface layer, with reduction of the metal oxide to a metal and oxidation of the aluminum diffusing out of the base material to aluminum oxide, and
formation of a brazed joint on the at least one metal sheet in the at least one brazing section.

### Claim 9 (depends on 8)

The process according to claim 8, which further comprises, after step v), carrying out a further coating process applying an exhaust gas treatment layer completely covering the surface layer in the at least one subregion.