Process to deposit a protective coating on the inner wall of a tube, and notably a gun barrel produced according to this process

1. A process of making a gun barrel, the process comprising the following steps:

providing a cylindrical sleeve,

placing a layer of thermo fusible material on an external surface of the cylindrical sleeve,

machining the cylindrical sleeve with the thermo fusible material thereon to give the cylindrical sleeve an external diameter that corresponds to an internal diameter of a tube,

positioning the cylindrical sleeve in the tube, and

heating the cylindrical sleeve from inside the cylindrical sleeve with no added powder using a localized heating means that is positioned within the sleeve to solder the cylindrical sleeve in the tube.

2. A process according to claim 1 , wherein the thermo fusible material has a melting point of between 600° C. and 1100° C.

3. A process according to claim 1 , wherein the cylindrical sleeve comprises a material having a melting point of more than 1850° C.

4. A process according to claim 1 , wherein providing a cylindrical sheet comprises:

rolling a sheet, and

welding edges of the sheet edge to edge to form the cylindrical sleeve.

5. A process according to claim 4 , wherein the welding is performed by electron beam or laser welding.

6. A process according to claim 1 , further comprising machining or sintering the cylindrical sleeve.

7. A process according to claim 3 , wherein the cylindrical sleeve is a material selected from the group consisting of Tantalum, Tungsten, Molybdenum, Chromium, Niobium, Hafnium, Vanadium, Zirconium, and their alloys.

8. A process according to claim 1 , wherein placing a layer of thermo fusible material on an external surface of the cylindrical sleeve comprises thermal projecting a thermo fusible material powder onto the external surface of the cylindrical sleeve.

9. A process according to claim 2 , wherein the thermo fusible material is selected from the group consisting of cobalt and nickel alloys.

10. A process according to claim 1 , wherein the thickness of the layer of thermo fusible material is about 1 mm.

11. A process according to claim 1 , wherein after placing the layer of thermo fusible material on said external surface of the cylindrical sleeve, the method further comprises re-melting the layer of thermo fusible material on the cylindrical sleeve before machining.

12. A process according claim 1 , wherein heating the cylindrical sleeve from inside the tube comprises heating with a plasma torch with transferred arc (PTA) with no added powder, with a relative rotating movement of the plasma torch with respect to the tube, combined with a relative translation of the plasma torch with respect to the tube.

13. A process according to claim 1 , wherein heating the cylindrical sleeve from inside the tube comprises cylindrically symmetrical heating.

14. A process according to claim 1 , wherein said heating comprises applying heat from a localized heat source inside the sleeve, and gradually moving said heat source longitudinally from one end to the other of the cylindrical sleeve.

15. A process according to claim 1 , wherein said heating comprises applying heat from a localized heat source inside the sleeve, and the heat source has a rotational movement and a translational movement.

16. A process according to claim 1 , wherein said heating comprises heating with a heat source that ensures cylindrically symmetrical heating.

17. A process according to claim 1 , wherein said heating includes no additional powder.