GB2440727A

GB2440727A - Build-up welding apparatus

Info

Publication number: GB2440727A
Application number: GB0615947A
Authority: GB
Inventors: Ben Anderson; Jeffrey Allen
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2006-08-11
Filing date: 2006-08-11
Publication date: 2008-02-13
Also published as: GB0615947D0

Abstract

Apparatus for depositing a material 22, 24 comprises a primary deposition head 2 and at least one secondary deposition head 4 each comprising a beam path for directing a high-energy beam 8, 8' at respective locations on a substrate 12 and a material source 18, 18' for supplying deposition material 16 to the respective locations. The at least one secondary deposition head 4 is functionally coupled to the primary deposition head 2 such that movement of the primary deposition head 2 relative to the substrate 12 creates an equivalent movement for the at least one secondary deposition head 4.

Description

WELDING APPARATUS

This invention concerns an apparatus and method for depositing a material on a substrate.

Apparatus and methods that allow direct metal deposition to a substrate are commercially available.

Direct metal deposition processes are high temperature processes that use multiple passes to deposit sequential layers onto a substrate. Each layer may have the same or different footprint to the other layers. In this way complex structures can be developed.

During the deposition process a laser or electron beam or such like is moved relative to the substrate and is directed at the substrate to create a traversing melt pool.

Material, either in powder or wire form, is deposited into the melt pool and melted. As the melt pool traverses away from the deposition location the material solidifies to form part of a layer of the structure. Subsequent deposition can be used to deposit further layers on the first layer. Once the structure is complete it may be machined to remove excess material and to provide a structure to a higher tolerance than may be achievable by the direct metal deposition alone.

Direct metal deposition is primarily used in low volume applications. Compared to other fabrication techniques, such as casting or machining, the equipment can be relatively expensive and the relative process times slow. It is therefore often not economical to change an existing production method for production volumes formed by direct metal deposition.

It is an object of the present invention to seek to provide an improved direct metal deposition apparatus and method that seeks to address these and other problems.

According to a first aspect of the invention there is provided apparatus for depositing a material comprising: a primary deposition head and at least one secondary deposition head functionally coupled to the primary deposition head such that movement of the primary deposition head creates an equivalent movement for the at least one secondary deposition head; characterised in that the primary and secondary deposition heads each comprise a beam path for directing a high-energy beam at respective locations on a substrate and a material source for supplying deposition material to the respective locations.

The apparatus may further comprises beam dividing means for dividing a high-energy beam between the beam path of the primary head and the beam path of the at least one secondary head.

The apparatus may comprise a beam generator for generating a high-energy beam.

The material source may be a powder head for supplying deposition material as a powder. The material source may be a wire spool for supplying deposition material as a wire.

The deposition material may be a nickel or titanium based alloy or superalloy.

According to a second aspect of the invention there is provided a method for depositing a material comprising: providing a primary deposition head and at least one secondary deposition head functionally coupled to the primary deposition head such that movement of the primary deposition head creates an equivalent movement for the at least one secondary deposition head; directing a high energy beam through each of the primary and secondary deposition heads to form respective melt pools on a substrate, directing a deposition material to the respective melt pools, and moving the primary deposition head to create an equivalent movement in the at least one secondary deposition head.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:-Fig. 1 depicts a powder fed laser deposition apparatus according to the invention Fig. 2 depicts a first beam path for directing a highenergy beam to the apparatus of Fig. 1 Fig. 3 depicts a second beam path for directing a high-energy beam to the apparatus of Fig. 1 Fig. 4 depicts an exemplary arrangement for two powder fed laser deposition heads Fig. 5 depicts an exemplary arrangement for four powder fed laser deposition heads.

Fig. 1 depicts a typical deposition head in accordance with the invention. A first head 2 is functionally coupled to a second head 4 by a support 6. Each head has a beam path through which a high-energy beam 8, 8' is passed and focussed by a lens 10, 10' onto a substrate 12.

A particularly suitable high-energy beam is created from a CO2 laser of type TR175O/380 coupled to a CNC control unit. Satisfactory results are obtained with the laser operating at a laser power between 144 and 432W and with a scanning speed between 200 to 400 mni/min. The laser is operated in pulse mode, the pulse frequency being set at 1kHz. The peak and trough of the pulse is set to 100% and 0% of the setting power respectively. In order to obtain the desired small focal spot of the laser beam, it may be required to position a beam expander (not shown) above the focal lens.

The energy of the beam forms a melt-pool in the substrate 12 into which a powder 16 is directed from a powder feed 18, 18'. Each of the deposition heads 2, 4 has a respective powder head 18, 18' . Each powder feed 18, 18' is focussed and aligned with the high-energy beam and thus the melt pool to deliver the deposition material thereto.

The deposition material is entrained within a supply of argon that shields the deposition location.

In normal operation the powder feed 18, 18' is in a fixed arrangement with the beam path however, alignment means 20, 20' are provided to tune the powder feed should it be determined that it is expedient to do so.

A controlled atmosphere is arranged around the melt pool to prevent contamination. An inert atmosphere of argon is preferred. The controlled atmosphere is maintained either by placing the deposition heads in an envelope containing the inert atmosphere, or more preferably by providing a more tailored enclosure that seals around the deposition heads 2, 4 and provides one or more limited enclosures around the deposition location.

Each of the deposition heads 2, 4 traverses relative to the substrate. Each head 2,4 is held in a fixed relation with the other head. One of the heads may be identified as a primary head, the location of which is determined by an optical sensor or other means. The remaining heads may be identified as secondary heads or slave heads, their location not being determined by an optical sensor, but rather being determined simply by their location relative to the primary head.

The first, primary head 2 moves relative to the substrate 12 to form a first component 22. The component is formed from a series of layers, with each layer being formed by solidification of powder injected into the melt pooi and allowed to cool by the passing of the high-energy beam. Each layer has a height of around 500pm. After a layer has been formed the primary head and consequently the secondary head is moved relative to the substrate a distance away from the substrate 12 that is equivalent to the depth of layer deposited to ensure the powder and beam remain directed and focused at the surface of the structure 22.

The movement of the heads relative to the substrate 12 is controlled by a CNC controller that acts against the support 6 to move the heads relative to a static substrate.

In alternative embodiment the heads are static and the controller moves the substrate.

Once each component 22, 24 is complete it is removed from the substrate 12. It may be necessary to mechanically dress the surfaces of the component to remove discontinuities or other minor tolerance discrepancies.

Whilst this embodiment has been depicted with the components being formed on a joined substrate it is possible to form each component on a separate substrate as would be understood by the skilled person. The substrate may also form part of a completed article and need not be planar.

A further advantage of the invention is in the reduced overhead costs, floor space required, number of machines and operators required, and the ability to multiply the functionality of expensive equipment. It has already been mentioned that expensive CNC equipment can control the location of multiple deposition heads. It is also possible to multiply the functionality of the high-energy beam generator.

It will be appreciated that each of the beams 8, 8' could be provided by a separate high-energy beam generator.

However, in a preferred embodiment, described with reference to Fig. 2, a beam 31 generated by a beam generator 30 is split between the deposition paths. A beam generator 30 generates a CO2 laser which passes through a first splitter 32 which divides the beam into a first component 8 and a second component 34. The first component is directed to the primary deposition head 2 and the second component is directed to a further splitter 35 that again divides the beam 34 into two further components 8' and 36.

The component 8' is directed to a secondary head and the component 36 passed to further splitters or optic elements to direct the component at additional secondary heads, where they are provided. It will be understood that if just two deposition heads are to be provided with a high-energy beam from a beam source 30 then the splitter 35 may be replaced with a simple optical directing element such as a mirror.

In the alternative embodiment shown in Fig. 3, the high-energy beam is split at the beam generator and passed to the beam path 8, 8' along a plurality of optical fibres 40, 42. Beneficially, the weight added to the deposition heads is minimal in this embodiment.

It will be appreciated that there is a wide choice in the arrangement of secondary heads to primary heads that may be used. Two exemplary embodiments are shown in Fig. 4 and Fig. 5. In both these arrangements a frame 50 extends around the deposition heads to provide stiffness. The heads may be arranged in a linear array, as in Fig. 4, or in an array that extends in a second dimension, as in Fig. 5 where the secondary heads 8' are located on spokes 6 radiating from a primary head. The spokes may be used to supply powder to the powder feeder.

Various modifications may be made without departing from the scope of the invention. For example, the apparatus and method has been described with reference to powder fed laser deposition. It is equally applicable to apparatus and methods where is deposition material is supplied in the form of a wire.

Similarly, though the laser source described is a CO2 laser the invention is equally applicable to other laser sources such as Nd:Yag lasers or other high energy beam sources such as electron beams.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS

1. Apparatus for depositing a material comprising: a primary deposition head and at least one secondary deposition head each comprising a beam path for directing a high-energy beam at respective locations on a substrate and a material source for supplying deposition material to the respective locations; characterised in that the at least one secondary deposition head is functionally coupled to the primary deposition head such that movement of the primary deposition head relative to a substrate creates an equivalent movement for the at least one secondary deposition head.

2. Apparatus according to claim 1, further comprising beam dividing means for dividing a high-energy beam between the beam path of the primary head and the beam path of the at least one secondary head.

3. Apparatus according to claim 1 or claim 2, further comprising a beam generator for generating a high-energy beam.

4. Apparatus according to any preceding claim, wherein the material source is a powder head for supplying deposition material as a powder.

5. Apparatus according to any one of claims 1 to 3, wherein the material source is a wire spool for supplying deposition material as a wire.

6. Apparatus according to any preceding claim, further comprising an alloyed deposition material.

7. Apparatus according to claim 6, wherein the alloyed deposition material is a nickel or titanium based superalloy.

8. Apparatus according to any preceding claim, wherein the apparatus further comprises a high-energy beam source.

9. Apparatus according to claim 8, wherein the apparatus further comprises a beam splitting means to split a beam generated by the high-energy beam source for supply to the deposition head and the at least one secondary deposition head.

10. Apparatus substantially as hereinbefore described with reference to Figures 1 to 5.

11. A method for depositing a material comprising: providing a primary deposition head and at least one secondary deposition head functionally coupled to the primary deposition head such that movement of the primary deposition relative to a substrate head creates an equivalent movement for the at least one secondary deposition head; directing a high energy beam through each of the primary and secondary deposition heads to form respective melt pools on a substrate, directing a deposition material to the respective melt pools, and moving the primary deposition head relative to its respective melt pool to create an equivalent movement in the at least one secondary deposition head.

12. A method substantially as hereinbefore described with reference to Figures 1 to 5