EP0237153A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Process for removing protective coatings and bonding layers from metal parts
Assignee: University of Dayton
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Filing: 1987-01-22
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Granted: —
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Expires: 2007-01-22
Abstract
Abstract A process for removing protective coatings and/or bonding layers from metal parts, particularly gamma prime hardened nickel base alloy, solid solution superalloy, iron base superalloy, and cobalt base superalloy parts to render them brazable or otherwise bondable. The process uses a C-O-H-F atmosphere as the primary stripping material wherein the atmosphere has a H/O ratio of 10 4 or greater. The preferred source of the C-O-H-F atmosphere is thermal decomposition of a fluorocarbon resin.
Inventors
- 👤 Jack W. Chasteen
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 18:52
CPC Classifications
C; C23; C23F; C23F1/00; C23F1/10; C23F1/12; C23F1/44; C23G; C23G5/00
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
140 words
A process for removing protective coatings and/or bonding layers from a base metal which comprises: providing an atmosphere containing the elements C, O, H and F in which the C/H ratio is greater than or equal to 0.125, the F/H ratio is greater than or equal to 0.025 and having a H/O ratio of 10 4 or greater; - subjecting said base metal to said atmosphere at a temperature of 500 to 900°C for a period of time sufficient to undermine said coating or bonding layer; replacing said atmosphere with CO 2; subjecting said base metal to said C0 2 for a period of time sufficient to remove any carbon deposited on said base metal while subjecting said base metal to said atmosphere without oxidizing said base metal; and removing said undermined coating or bonding layer from said base metal.
Claim 2
Dependent Claim
140 words
A process for removing protective coatings and/or bonding layers from a base metal which comprises: providing an atmosphere containing the elements C, O, H and F in which the C/H ratio is greater than or equal to 0.125, the F/H ratio is greater than or equal to 0.025 and having a H/O ratio of 10 4 or greater; - subjecting said base metal to said atmosphere at a temperature of 500 to 900°C for a period of time sufficient to undermine said coating or bonding layer; replacing said atmosphere with CO 2; subjecting said base metal to said C0 2 for a period of time sufficient to remove any carbon deposited on said base metal while subjecting said base metal to said atmosphere without oxidizing said base metal; and removing said undermined coating or bonding layer from said base metal.
Claim 3
Dependent Claim
17 words
A process according to claim 1 wherein said undermined coating or bonding layer is removed by grit-blasting.
Claim 4
Dependent Claim
26 words
A process according to claim 1 or claim 2, wherein said step of providing said atmosphere containing C, O, H and F comprises pyrolyzing a fluorocarbon.
Claim 5
Dependent Claim
11 words
A process according to claim 3, wherein said fluorocarbon is polytetrafluoroethylene.
Claim 6
Dependent Claim
54 words
A process according to claim 4, wherein said base metal is subjected to said atmosphere at a temperatue of 500 to 600°C until such time as said polytetrafluoroethylene is fully pyrolized, whereafter, said base meal is subjected to said atmosphere at 700 to 800°C until said coating or bonding layer is removable by grit-blasting.
Claim 7
Dependent Claim
41 words
A process according to any preceding claim, wherein said base metal is subjected to said atmosphere for a period of time sufficient to undermine said coating or bonding layer and to remove passivating oxides from the surface of said base metal.
Claim 8
Dependent Claim
48 words
A process according to claim 6 wherein after subjecting said base metal to CO 2 , said process comprises the additional step of subjecting said base metal to an atmosphere consisting essentially of hydrogen to reduce any CrF 3 on the surface of said base metal to Cr.
Claim 9
Dependent Claim
26 words
A process according to claim 7, wherein said base metal is subjected to said atmosphere consisting essentially of hydrogen at a temperature of 900 to 1000°C.
Claim 10
Dependent Claim
18 words
A process according to any one of claims 1 to 7, which is carried out at atmospheric pressure.
Claim 11
Dependent Claim
30 words
A process according to any preceding claim, wherein said base metal is selected from solid solution superalloys, gamma prime hardened nickel base alloys, cobalt base superalloys, and iron base superalloys.
Claim 12
Dependent Claim
17 words
A process according to any preceding claim, wherein said protective coating is a metallic or oxide coating.
Claim 13
Dependent Claim
19 words
A process according to claim 11, wherein said protective coating is an aluminide, a chromium-aluminide or a nickel-aluminide coating.
Claim 14
Dependent Claim
13 words
A process according to claim 11, wherein said coating is a chromium-aluminium coating.
Claim 15
Dependent Claim
14 words
A process according to claim 11, wherein said protective coating is a zirconium-oxide coating.
Claim 16
Dependent Claim
21 words
A process of any preceding claim, wherein said bonding layer is a gamma prime bonding layer, or a chromium-aluminium- yttrium layer.
Claim 17
Dependent Claim
116 words
A process for removing protective coatings and/or bonding layers from a base metal which comprises: providing an atomosphere containing the elements C, O, H and F by pyrolyzing a polytetrafluoroethylene resin, said atmosphere having a H/O ratio of 10 4 or greater; subjecting said base metal to said atmosphere at a temperature of 500 to 900°C for a period of time sufficient to undermine said coating or bonding layer; replacing said atmosphere with C0 2 ; subjecting said base metal to-said-C02 for a period of time sufficient to remove any carbon deposited on said base metal while subjecting said base metal to said atmosphere; and removing said undermined coating or bonding layer from said base metal.
Claim 18
Dependent Claim
116 words
A process for removing protective coatings and/or bonding layers from a base metal which comprises: providing an atomosphere containing the elements C, O, H and F by pyrolyzing a polytetrafluoroethylene resin, said atmosphere having a H/O ratio of 10 4 or greater; subjecting said base metal to said atmosphere at a temperature of 500 to 900°C for a period of time sufficient to undermine said coating or bonding layer; replacing said atmosphere with C0 2 ; subjecting said base metal to-said-C02 for a period of time sufficient to remove any carbon deposited on said base metal while subjecting said base metal to said atmosphere; and removing said undermined coating or bonding layer from said base metal.
Claim 19
Dependent Claim
52 words
A process according to claim 16 wherein said base metal is subjected to said atmosphere at a temperature of about 500 to 600°C until such time as said polytetrafluoroethylene is fully pyrolyzed, whereafter said base metal is subjected to said atmosphere at 700 to 800°C until said coating is removable by grit-blasting.
Claim 20
Dependent Claim
40 words
A process according to claim 17, wherein said base metal is subjected to said atmosphere for a period of time sufficient to undermine said coating or bonding layer and to remove passivating oxides from the surface of said base metal.
Claim 21
Dependent Claim
48 words
A process according to claim 18, wherein after subjecting said base metal to C0 2 , said process comprises the additional step of subjecting said base metal to an atmosphere consisting essentially of hydrogen to reduce any CrF 3 on the surface of said base metal to Cr.
Claim 22
Dependent Claim
26 words
A process according to claim 19, wherein said base metal is subjected to said atmosphere consisting essentially of hydrogen at a temperature of 900 to 1000°C.
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