GB2194552A

GB2194552A - Joining by electrolytic or electroless deposition

Info

Publication number: GB2194552A
Application number: GB08621071A
Authority: GB
Inventors: John Foster; Francis John Honey; Eric Charles Kedward; Vernon Maurice Wride
Original assignee: Baj Ltd
Current assignee: Baj Ltd
Priority date: 1986-09-01
Filing date: 1986-09-01
Publication date: 1988-03-09
Also published as: GB8621071D0

Abstract

A method of joining two metal components comprises placing the components in adjacent or touching relationship and producing by electrolytic or electroless deposition a deposit which is bonded to them both. The method is particularly suitable for producing by electroforming articles which have undercuts and may be used with materials which are difficult to weld such as superalloys. A method of manufacturing a tube having an inwardly and axially directed flange 4 thereon to produce an undercut groove 2 comprises electroforming on a mandrel (6, Fig. 2) a first component (5) having a portion of a shape to form part of the tube and, extending from one end thereof, a second portion (11) of a shape to form the flange and electroforming, on a second and hollow mandrel (8) a second component (7) in the form of a shape to form the remainder of the tube, telescoping the second mandrel (8) over the second portion (11) of the first component, preparing a groove (14. Fig. 3) in the adjacent regions of the first portion (5) of the first component and the second component, producing by electrodeposition a deposit in the groove, and removing the mandrels (6, 8). The method may be used to make the vaporiser tube of a combustion chamber for a gas turbine engine. <IMAGE>

Description

SPECIFICATION Joining of metal components This invention relates to the joining of metal components and according to its broadest aspect comprises the joining of two metal components by placing the components in adjacent or touching relationship and producing by electrodeposition a deposit which is bonded to both of them. The process may be likened to a welding process in which weld metal is deposited to form a welded joint but deposition is effected by an electrodeposition process rather than by heat. The term electrodeposition is intended to cover both electrolytic and electroless deposition although the former will be used in the majority of applications since it is more suitable for depositing considerable volumes of material.

The materials of the two components and of the deposit may all be different. Alternatively only two materials may be involved so that either the two components may be of the same material and the deposit of a different material or the deposit may be of the same material as one of the components with the other component of a different material. Preferably, however, the two components and the deposit will be of the same material.

The process may be used for joining components which are difficult or impossible to join by conventional methods such as by any of the various welding techniques which are available. Thus the process may be used for joining components made from superalloys or superalloy-type materials. Examples of materials which may be joined include high strength, high temperature alloys based on nickel and/or cobalt, and, generally, alloys based on cobalt, nickel, chromium or tungsten and, more particularly, cobalt chromium carbide and tungstem carbide.The deposit may be of a material incorporating particles co-deposited from the bath and examples of such materials are given in our British Patent Specifications Nos. 1218179, 1329081, 1358538, 2014189, 2083076 and 2167446 which are incorporated herein by reference and to which reference may be made for further details of the materials and of processes which may be employed to produce the deposit. As is explained in these specifications, the co-deposited particles may remain in substantially their co-deposited state in the finished article but more usually they are modified or completely eliminated during a subsequent heat treatment during which diffusion occurs in one or both directions between the particles and the matrix.

The components to be joined may be produced by any of the usual methods including rolling, forging, casting and powder-metallurgy techniques but the invention is particularly applicable to the joining of electroformed components. One application of the invention is to the manufacture of an article incorporating an undercut; thus the article can be made in two parts each of which can be produced without an undercut and the two parts are then joined by the process of the invention. This is particularly suitable for parts to be made by electroforming where the production of undercuts is impossible or at least requires elaborate jigging and complex electrodes. The electroforms may consist of the materials and be produced by the processes described in the above-identified British Patent Specifications.

The invention may be carried into practice in various ways but the production of one component or article using a process embodying the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a fragmentary longitudinal section of a body of revolution produced by the process; Figure 2 shows parts of two mandrels used in the process; and Figure 3 shows an intermediate stage in the manufacturing process.

Fig. 1 shows part of one wall of a body of revolution which in this case is a vaporiser tube of a combustion chamber for a gas turbine engine. The component comprises a circular cylindrical wall 1 on the interior of which there is formed an axially facing groove 2 by means of an inwardly directed inclined annular wall 3 and an inner cylindrical wall 4 which extends parallel to and coaxial with the wall 1.

As will be explained, the component is manufactured by electroforming from an alloy which, after heat treatment, comprises 20% chromium, 6% tungsten, 0.2% carbon and the balance cobalt. It will be appreciated that by normal electroforming processes it would be difficult or impossible to produce the component shown in Fig. 1 because of the presence of the groove 2 forming an undercut. In accordance with the present invention, the component is produced in two parts which are then connected together by an electroformed deposit.

As a first step, an electrodeposit 5 of a composite material is produced on the outer surface of an aluminium mandrel 6 of the shape shown in Fig. 2 by one of the processes described in the aforementioned British Patent Specifications, for example that described in British Patent Specification number 2014189. As a second step, an electrodeposit 7 of the same thickness as the electrodeposit 5 is produced in a similar manner to that electrodeposit on the outer surface of a cylindrical aluminium mandrel 8.The outer tapering surface 9 and the outer cylindrical surface 11 of lesser diameter of the electroformed coating 5 are machined to precisely conform to the inclined surface 12 and the inner cylindrical surface 13 respectively of the cylindrical mandrel 8 and the mandrel 8 is then offered up to the mandrel 6 to form a tight telescoped connection between the two elements each of which comprises a mandrel and a coating thereon. The adjacent regions of the composite coatings 5 and 7 are then ground to form a groove 14 in a similar manner to the dressing by which a weld seam is prepared. This produces the condition shown in Fig. 3 and it will be noted that the groove 14 is sufficiently deep to produce a feather edge 15 in the coating 7 leading to the point of contact with the coating 5.The cylindrical surface of the coating 5 to the left of the groove 14 as seen in Fig. 3 and the cylindrical surface of the coating 7 to the right of the groove 14 as seen in Fig. 3 are then masked and a bead of material is then formed by electrodeposition in the groove 14, the material being deposited being the same as that which was deposited to form the coatings 5 and 7.

The surfaces of the groove 14 will of course be clean and grease free and prepared in the usual manner for depositing, a material which is to bond with the substrate. Deposition of material in the groove will produce a bead similar to a weld bead and this can be dressed by machining as required and in the particular example being described the bead is ground down until its surface is coincident with the cylindrical surface of the coatings 5 and 7. The aluminium mandrels 6 and 8 are then dissolved out with caustic material to leave the single article shown in Fig. 1. This article is then heat treated to produce diffusion between the particles and the matrix as described above, the final article having the composition set out above.

It will be understood that a substantially unitary and homogeneous article has been produced by first producing two elements or components by electroforming by electroforming a connecting bead using the same material as that from which the two components were formed.

Claims

1. A method of joining two metal components which comprises placing the components in adjacent or touching relationship and producing by electrodeposition (as herein defined) a deposit which is bonded to them both.

2. A method as claimed in Claim 1 in which the deposit is of the same material as one of the components.

3. A method as claimed in Claim 1 in which the deposit and both of the components are of the same material.

4. A method as claimed in Claim 1 or Claim 2 or Claim 3 in which the material of at least one of the components is a superailoy.

5. A method as claimed in Claim 1 or Claim 2 or Claim 3 in which the material of at least one of the components is of cobalt chromium carbide and/or tungsten carbide.

6. A method as claimed in any of the preceding Claims in which the deposit incorporates co-deposited particles.

7. A method as claimed in Claim 6 which includes heat treating of the deposit to produce diffusion between the particles and the matrix.

8. A method as claimed in any of the preceding Claims in which at least one of the components is an electroform.

9. A method as claimed in any of the preceding claims in which the article produced by the joining incorporates an undercut.

10. A method of manufacturing an article incorporating an undercut which comprises producing by electroforming two components, neither of which incorporates an undercut, placing the components in adjacent or touching relationship and producing by electrolytic deposition a deposit which is bonded to both components.

11. A method as claimed in Claim 10 in which the article is a tube on the interior of which there is an axially facing groove constituting the undercut.

12. A method of manufacturing a tube having an inwardly and axially directed flange thereon to produce an undercut groove, the method comprising electroforming on a mandrel a first component having a portion of a shape to form part of the tube and, extending from one end thereof, a second portion of a shape to form the flange and electroforming, on a second and hollow mandrel, a second component in the form of a shape to form the remainder of the tube, telescoping the second mandrel over the second portion of the first component, preparing a groove in the adjacent regions of the first portion of the first component and the second component, producing by electrodeposition (as herein defined) a deposit in the groove, and removing the mandrels.

13. A method as claimed in Claim 12 in which the mandrels are aluminium.

14. A method as claimed in Claim 12 or Claim 13 in which the two components and the deposit comprise cobalt, chromium, tungsten and carbon.

15. A method of joining two metal components substantially as specifically described herein with reference to the accompanying drawings.