GB2208490A

GB2208490A - A method of manufacturing components from metallic or non-metallic powder

Info

Publication number: GB2208490A
Application number: GB8818779A
Authority: GB
Inventors: Wolfgang Betz
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: MTU Aero Engines AG
Priority date: 1987-08-07
Filing date: 1988-08-08
Publication date: 1989-04-05
Anticipated expiration: 2008-08-08
Also published as: GB2208490B; DE3726259C1; FR2619035A1; FR2619035B1; GB8818779D0

Description

2r) 1- 0 8 4 9 J i 1 M&C FOLIO: 230P56737 WANGDOC: 0814k A method of

manufacturing components from metallic or nonmetallic powder This invention relates to a method of manufacturing components from metallic or non-metallic powder which is isostatically pressed in a malleably yielding mould.

In this connection. the moulding can be effected by the following methods:

a) Axial pressing in stamping dies, b) Cold isostatic pressing in flexible moulds, c) Metal injection moulding and d) Hot isostatic pressing in malleably workable sheet metal shells or in breakable ceramic moulds.

_With the methods a). b) and c) listed above. powders are used to which greater or lesser amounts of binding agent are added: this must be burnt out before the sintering process which is necessary here. With hot isostatic pressing on the other hand, powder which is free of binding agent is compressed directly into its final shape. In this case however. it is necessary that the mould material withstands the high temperatures of the compression process.

f 2 Alongside certain advantages, these known manufacturing processes also have certain disadvantages. For example. in the case of axial pressing. expensive and delicate die pressing tools are necessary. The obtainable dies for the blanks to be manufactured are restricted longitudinally in the direction of pressing, particularly by the necessity to shift the pressing die basically along one axis. For areas of a component which are of different height or length. complicated die movements are required. The thickness obtainable in the component during production can also turn out very differently.

Only relatively roughly-shaped components can be manufactured by means of cold isostatic compression in flexible moulds. Undercuts. fractures and narrow fissures in the component particularly cause problems here.

It is true that with a sufficient tool expenditure. metal injection moulding can be used to manufacture components having a high degree of filigree and complex shapes; however in this case a very high proportion of binding agent is required in the mass to be injected. On the other hand. this means very long burning out times and a limitation in the wall thickness of the components manufactured. Due to the necessity for the 1 3 moulding material to flow into the tool mould in one stream and at a constant temperature. the maximum dimensions of a component are additionally restricted.

Hot isostatic pressing basically involves the disadvantage that the fixing of the desired shape only takes place at high temperatures, that is to say the mould material must still remain leakproof and inherently stable at these temperatures. This restriction means that only largish shapes can be produced, and/or very high costs must be accepted for the production.

An object of the invention is to provide a method of manufacturing components which avoids the disadvantages of the known methods and. particularly, allows the mass production of components consisting of metallic and non-metallic powders, the method operating true to size. efficiently and in particular economically in its stages. with a relatively low expenditure of manufacturing materials.

Claims

The invention provides a method as claimed in Claim The particular advantage of the invention is in principle to be found on the one hand in the simple manufacture of the split basic mould for producing the 4 dead pattern. which basic mould can be used repeatedly, and on the other hand in the closed and waste-free production cycle for these intermediate patterns and for the pattern shells. whose materials can be reused. The invention allows the manufacture. in several stages. by means of pressing. of components made of metallic or non-metallic powders with great accuracy. and repeated use of the means used. that is to say with. often repeatable. use of the materials for the dead patterns and pattern shells The invention will now be described with reference to the accompanying drawing which shows. step by step. by means of a flow diagram. an embodiment of the method according to the invention. The course of this manufacturing method is explained in more detail as follows. In the drawing, a basic pattern 1 is first produced by the usual methods of pattern manufacture; the basic pattern 1 is made of a material which can be easily worked and is enlarged to take into account subsequent contraction. A split reusable basic mould 2 is then manufactured e.g. by means of recasting with silicon rubber. this basic mould 2 serving to produce dead patterns 3. For this an easily soluble substance M, e.g. nickel nitrate, is melted. this material being molten at a temperature higher than 1000C and solid at a temperature lower than 500C. The then moulded dead pattern 3 is dipped. in the solid state. into a molten coating material H, particularly wax. this coating material solidifying at room temperature, so that a coated dead pattern 4 is formed. With the help of a solvent L. the dead pattern 4 or rather its material M is washed out. this material returning again to the production cycle. the solvent L being separated and reused. The mould shell 5 thus produced, made out of the coating material H. particularly wax, is then filled with a powder P out of which the component is to be manufactured. this powder being with or without a binding agent B. Subsequently, the filling F in the mould shell 5. which has been previously brought to a suitable temperature to avoid cracks in the mould and to make possible malleable working. is compressed by isostatic cold pressing to the extent that the powder particles. if necessary with the help of a binding agent B which is added in small amounts. are joined to each other sufficiently firmly for their shape to be maintained subsequently. The coated green compact 6 produced then becomes the green compact 61 without a casing or mould shell 5. by melting off of the mould shell 5 or the coating material 4 6 H, this returning to the production process again. The remains of the coating are then evaporated from the green compact 61 and the binding agent B is also burnt out; in addition pre-sintering takes place. The resulting green compact 611 is final sintered to the component BT. If required. the component BT can be secondarily compressed by means of isostatic hot pressing (Component BT') 7 claims:

1. A method of manufacturing components from metallic or non-metallic powder, comprising the following steps:

a) manufacturing a dead pattern of the desired component. the dead pattern being enlarged by the extent of subsequent contraction and being made of a material soluble at room temperature in a solvent and being manufacured by melting and then casting in a reusable split basic mould, the said material being molten at a temperature higher than 1000C and solid at a temperature lower than 500C, b) manufacturing a mould shell by coating the dead pattern with a material which is malleably workable during subsequent isostatic pressing. particularly wax, this material forming a solid mould shell at room temperature, C) washing the said material of the dead pattern out of the mould shell by means of a solvent.

d) filling the mould shell with powder to which. if necesary. a binding agent is added.

e) bringing the mould shell filled with powder to 8 a temperature suitable for subsequent mould pressing.

f) isostatically pressing of the powder in the mould shell to form a pressed green compact, g) removing the mould shell from the pressed green compact. and 1 h) if necessary, burning out the binding agent from the green compact. and sintering the green compact.

2. A method as claimed in claim 1, wherein the dead pattern is divided into several pattern parts which are manufactured separately from each other according to the method step a) and are subsequently securely joined together. particularly by adhesion.

3. A method as claimed in claims 1 or 2. wherein the sintered and/or finished component is also secondarily compressed by isostatic hot pressing.

4. A method as claimed in any one of the preceding claims. wherein the green compact is also machined before the burning out and sintering.

5. A method as claimed in any one of the preceding claims, wherein the softening temperature of the binding 9 9 agent is above the melting temperature of the mould shell which consists of wax.

6. A method as claimed in claim 5. wherein the wax for manufacturing the mould shell is inherently stable at room temperatures between approximately 15 - 300C and is sufficiently ductile at room temperatures between approximately 45 and 600C to absorb the occurring deformations during isostatic cold pressing without breaking and can melt at temperatures under 1000C.

7. A method as claimed in any one of the preceding claims, wherein the solution arising from washing out the said material of the dead pattern is treated to retrieve the material and the solvent. which are then reused.

8. A method as claimed in any one of the preceding claims, wherein the a basic mould is made of silicon rubber.

9. A method as claimed in any one of the preceding claims, wherein the material for the dead pattern is nickel nitrate.

10. A method as claimed in any one of the preceding claims. wherein a nickel-based alloy is used as a powder i for manufacturing the component.

11. A method as claimed in any one of the preceding claims. wherein a titanium-based alloy is used as a powder for manufacturing the component.

12. A method as claimed in claim 2. wherein an iron-based alloy is used as a powder for manufacturing the component.

13. A method as claimed in any one of the preceding claims. wherein ceramic powder is used as a powder for manufacturing the component.

14. A method as claimed in any one of the preceding claims. wherein the dead pattern is provided with a separating layer before the construction of the mould shell.

15. A method of manufacturing components from metallic or non-metallic powder substantially as herein described with reference to the accompanying drawing.

16. Components manufactured by a method as claimed in any one of the preceding claims.

Published 1958 at Mte Patent Office. Sa:,c House 66 -'- H.----. London WCIR 4TP Flurther copies may be obtained from The Paten, Offf,-_E Sales Branch, St Mary Cray. Orpington. Kent BR5 3RD- Printed ky Multiplex techniques Itd, St Mary Crky. Kent. Con. 1 Z7_ c