Hot isostatic pressing consolidation of powder derived parts

1. A method of forming a metal component from metal powder, the method comprising:

(a) exposing the metal powder to an inert gas;

(b) consolidating the metal powder into a solid metal;

(c) exposing the solid metal to a hot isostatic pressing process to form a metal component, wherein the hot isostatic pressing process comprises one initial compression cycle followed by at least one decompression and recompression cycle; and

(d) decompressing to second pressure that is sufficient for diffusion to occur, but insufficient for bubble collapse.

2. The method according to claim 1 , wherein the one initial compression cycle comprises increasing a temperature of the hot isotactic pressing process to a first temperature and wherein the method further comprises maintaining the first temperature throughout steps (c) and (d).

3. The method according to claim 2 , wherein step (d) comprises holding the second pressure whilst maintaining the first temperature, and wherein the method further comprises (e) reducing the second pressure to atmospheric pressure or below, at the same time as reducing the first temperature to room temperature.

4. The method according to claim 1 , wherein steps (a) and (b) are part of a primary hot isostatic pressing method or an additive layer manufacturing method.

5. The method according to claim 4 , wherein the additive layer manufacturing method is selective laser melting.

6. The method according to claim 1 , wherein the metal powder is selected from the group consisting of nickel, cobalt, titanium, iron, aluminium, and alloys thereof.

7. The method according to claim 1 , wherein the inert gas is soluble in the solid metal.

8. The method according to claim 1 , wherein the inert gas is helium and the metal powder is an alpha, beta, or alpha-beta titanium alloy.

9. The method according to claim 1 , wherein the one initial compression cycle comprises increasing a pressure to a first pressure between 100 to 300 MPa and increasing a temperature to a first temperature between 500 to 1500° C.

10. The method according to claim 9 , wherein the first pressure and first temperature are held for a period of time ranging from 30 to 120 minutes.

11. The method according to claim 9 , wherein the at least one decompression and recompression of step (c) comprises reducing the first pressure to atmospheric pressure or below followed by increasing the pressure back to a third pressure, which third pressure is substantially the same as the first pressure, and wherein the first temperature is maintained throughout the at least one decompression and recompression step.

12. The method according to claim 11 , wherein the atmospheric pressure or below is held for a period of time ranging from 5 to 120 minutes.

13. The method according to claim 11 , wherein the third pressure is held for a period of time ranging from 30 to 120 minutes.

14. The method according to claim 11 , wherein step (d) comprises lowering the third pressure to the second pressure and holding the second pressure for a period of time ranging from 30 to 120 minutes, before lowering the second pressure to atmospheric pressure or below.

15. An aircraft component produced by the method according to claim 1 .

16. A method of forming a metal component from metal powder, the method comprising:

(a) exposing the metal powder to an inert gas;

(b) consolidating the metal powder into a solid metal;

(c) exposing the solid metal to a hot isostatic pressing process to form a metal component, wherein the hot isostatic pressing process comprises one initial compression cycle followed by at least one decompression and recompression cycle; and

(d) decompressing to a second pressure that is sufficient for diffusion to occur, but insufficient for bubble collapse,

wherein step (d) is carried out after bubbles present in the solid metal have almost collapsed.