NET-SHAPE OR NEAR NET-SHAPE POWDER ISOSTATIC PRESSING PROCESS

Abstract

A method of producing a net or near net-shape component from metal powder comprises producing an insert of accurate dimensions corresponding to the dimensions of a bore to be created in the finished component, the bore having a length of at least 750 mm, supporting the insert within a mould cavity, filling the mould cavity with metal powder, subjecting the powder to isostatic pressing, and subsequently removing the material of the insert. The mould can be an independent mould that is removed after an initial step to bind the powder together into a pre-form, and the pre-form is then encapsulated in a suitable containment, such as a canister or a sprayed coating. The insert can be a metallic insert of a material, such as copper, that is subsequently removable by chemical etching. The insert can be coated with a material that is amenable to removal by etching, and to enable the insert to be extracted. A metallic insert can be coated with a material that provides a diffusion barrier to prevent the material of the insert from diffusing by atomic diffusion into the powder being consolidated during HIPing.

Description

The invention relates to net-shape or near net-shape powder isostatic pressing processes, as applied to metallic and/or cermet/MMC (metal matrix composites) powder.

The invention is concerned particularly, but not exclusively, with the production of a bore of substantial length, typically longer than 750 mm, in a component of hard wear-resistant material.

Such components can be made by Hot Isostatic Pressing (HIPing) but it is extremely difficult to produce bores in the formed components by machining. With difficulty, straight bores of small length such as 10 mm can be machined.

We consider that it would be of advantage in certain circumstances to provide a bore of accurate dimensions extending lengthwise through a component of length approximately 2 m, the component desirably being produced from a powder by a hot isostatic pressing process so as to provide hard wearing properties.

According to one aspect of the invention a method of producing a net or near net-shape component from metal powder comprises producing an insert of accurate dimensions corresponding to the dimensions of a bore to be created in the finished component, the bore having a length of at least 750 mm, supporting the insert within a mould cavity, filling the mould cavity with metal powder, subjecting the powder to isostatic pressing, and subsequently removing the material of the insert.

As is well known, the mould may be an independent mould that is removed after an initial step to bind the powder together into a pre-form, and the pre-form is then encapsulated in a suitable containment which may be a canister or a sprayed coating, or a canister of suitable internal shape may be used as the mould, and the canister itself is evacuated prior to HIPing

Preferably the insert is supported in position in the mould cavity by a plurality of formers of a material that is compatible with the finally consolidated powder.

The insert may be a metallic insert of a material that is subsequently removable by chemical etching, preferably copper. The chemical etching may be assisted by electrolytic reaction.

In suitable cases the insert need only be coated with a material that can subsequently be removed by etching, in order to release the insert, which can then be extracted.

Preferably the metallic insert is coated with a suitable material that provides a diffusion barrier to prevent the material of the insert from diffusing by atomic diffusion into the powder being consolidated during HIPing.

The invention can enable a helical bore to be provided in a component.

Such a helical bore could be used for various purposes, such as to convey a fluid and/or to accommodate an electrical or fibre-optic cable to provide sensor or control system communications for example.

In one preferred embodiment a copper rod, of a diameter in the range of 6 to 10 mm for example and of length greater than 2 m, is first bent into a helix of the required dimensions and this is then held in position in a powder containment prior to filling the containment with powder. The containment enclosing the powder, rod and former, is then consolidated by solid state diffusion using the HIPing method.

The diffusion barrier may be Al₂O₃ applied by vapour phase deposition or by high velocity spraying. Alternatively, the diffusion barrier may be created by applying boron nitride as an aqueous solution by spraying.

In a second embodiment a preformed metal tube, of 6 mm to 10 mm diameter for example, is filled with ceramic particles and is bent to a helical shape and placed within the powder containment prior to filling the containment with powder. The tube is held in position with formers compatible with the finally consolidated powder. The entire containment encompassing the metallic and/or cermet/MMC powder is then consolidated by solid state diffusion using the HIPing method.

During consolidation the metal tube may become totally diffusion bonded into the consolidated component but the ceramic particles will remain in the pre-process particle form and thereby can be removed mechanically via vibration techniques to leave a clean hole through the component.

EXAMPLE

The invention can be used to provide one or more holes in one or more helical lobes provided internally of the stator body of a helicoidal positive displacement pump, the stator body having a length of as much as 2 m or more. Such stator bodies can be used to form the radially outer part of a linear motor and/or mud pump used in down-hole drilling. The hole or holes can be positioned to follow the core of a helical flute, which may have a pitch of about 1 m and a radius of 50 mm about the body axis. The helical lobes are defined by helical grooves in a mandrel that is positioned in the mould during pressing of the stator body.

Claims

1. A method of producing a net or near net-shape component from metal powder comprising producing an insert of accurate dimensions corresponding to the dimensions of a bore to be created in the finished component, the bore having a length of at least 750 mm, supporting the insert within a mould cavity, filling the mould cavity with metal powder, subjecting the powder to isostatic pressing, and subsequently removing the material of the insert.

2. The method of claim 1 in which the mould is an independent mould that is removed after an initial step to bind the powder together into a pre-form, and the pre-form is then encapsulated in a suitable containment.

3. The method of claim 2 in which the containment is a canister.

4. The method of claim 2 in which the containment is a sprayed coating.

5. The method of claim 1 in which the insert is supported in position in the mould cavity by a plurality of formers of a material that is compatible with the finally consolidated powder.

6. The method of claim 1 in which the insert is a metallic insert of a material that is subsequently removable by chemical etching.

7. The method of claim 6 in which the insert comprises copper.

8. The method of claim 7 in which the chemical etching is assisted by electrolytic reaction.

9. The method of claim 1 in which the insert is coated with a material that is amenable to removal by etching, and comprising the steps of releasing the insert by etching the coating, and then extracting the insert.

10. The method of claim 6 in which the metallic insert is coated with a material that provides a diffusion barrier to prevent the material of the insert from diffusing by atomic diffusion into the powder being consolidated during HIPing.

11. The method of claim 10 in which the diffusion barrier comprises Al2O3 applied by vapour phase deposition.

12. The method of claim 10 in which the diffusion barrier comprises Al2O3 applied by high velocity spraying.

13. The method of claim 10 in which the diffusion barrier is created by applying boron nitride as an aqueous solution by spraying.

14. The method of claim 1 in which the insert is produced by taking a copper rod, of a diameter in the range of 6 to 10 mm and of length greater than 2 m, bending the copper rod into a helix of the required dimensions, and then holding the helical rod in position in a powder containment prior to filling the containment with powder, the containment enclosing the powder, rod and former, and then consolidating the powder by solid state diffusion using a HIPing method.

15. The method of claim 1 in which the insert is produced by taking a preformed metal tube, of 6 mm to 10 mm diameter, filling the tube with ceramic particles, and bending the filled tube to a helical shape, placing the helical filled tube within the powder containment prior to filling the containment with powder, holding the tube in position with formers compatible with the finally consolidated powder, providing a containment encompassing the metallic and/or cermet/MMC powder, and then consolidating the contained material by solid state diffusion using a HIPing method.

16. The method of claim 15 comprising removing the ceramic particles mechanically by a vibration technique to leave a clean hole through the finished component.

17. A net or near net-shape component produced by the method of claim 1.