Gun barrel liner, and additive method of making

Abstract

A method making a gun barrel liner includes depositing material on a mandrel that has ribs or ridges corresponding to the rifling grooves in the liner. The material may be deposited using plasma spraying, with sprayed splats of material re-melted after deposition for at least part of the deposition process to reduce or eliminate porosity in the deposited material. The mandrel may be made of metal, such as a high thermal conductivity metal such as copper. The mandrel may have a channel therein or therethrough. The channel may facilitate flow of liquid though the mandrel, one example of such a liquid being a coolant (such as water), used to remove heat produced during the material deposition. Another liquid passed through the channel may be an etchant (or other fluid) that is used to dissolve or otherwise remove the mandrel after the material of the gun barrel liner has been deposited.

1 . A method of making a gun barrel liner with rifling, the method comprising:
 depositing material onto a ridged outer surface of the mandrel to form the gun barrel liner, wherein the ridged outer surface corresponds to the rifling; and   while depositing the material, cooling the mandrel by passing coolant through a channel in the mandrel.   
     
     
         2 . The method of  claim 1 ,
 wherein the channel is along a longitudinal axis of the mandrel; and   wherein the cooling includes passing the coolant from one longitudinal end of the mandrel to an opposite longitudinal end of the mandrel.   
     
     
         3 . The method of  claim 1 , wherein the coolant is water. 
     
     
         4 . The method of  claim 1 , further comprising, following the depositing, chemically removing the mandrel. 
     
     
         5 . The method of  claim 4 , wherein the chemically removing includes passing an etchant through the channel to remove the mandrel. 
     
     
         6 . The method of  claim 1 , wherein the depositing includes plasma deposition. 
     
     
         7 . The method of  claim 6 , wherein the depositing includes re-melting at least some of the material after the material is deposited, thereby producing re-melted material with reduced porosity of the material. 
     
     
         8 . The method of  claim 7 , wherein the re-melting includes re-melting inner material of the liner having a thickness at least that of an expected wear thickness of the liner. 
     
     
         9 . The method of  claim 8 , wherein the depositing includes plasma deposition of additional material onto the re-melted material, where the additional material has greater porosity than the re-melted material. 
     
     
         10 . The method of  claim 6 , further comprising, prior to the plasma deposition, depositing a protective material onto the mandrel, with the protective material having a higher melting temperature than material of the mandrel. 
     
     
         11 . The method of  claim 10 , wherein the depositing the protective material includes deposition of the protective material using one or more of electroplating, chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma, or sputtering. 
     
     
         12 . The method of  claim 1 , wherein the depositing material includes depositing a material selected from the group consisting of chromium and alloys of chromium including nickel and/or cobalt. 
     
     
         13 . The method of  claim 1 ,
 wherein the method is part of a method of making a gun barrel, the method of making the gun barrel further comprising:   mechanically coupling the gun barrel liner to a cylindrical jacket that is outside of and surrounds the liner.   
     
     
         14 . A gun barrel liner comprising:
 an inner layer of material with relatively low porosity; and   an outer layer of material, surrounding the inner layer, wherein the outer layer has relatively high porosity;   wherein the inner layer of material has rifling grooves.   
     
     
         15 . The gun barrel liner of  claim 14 , wherein the inner layer and the outer layer are made of the same material. 
     
     
         16 . The gun barrel liner of  claim 14 , wherein the layers are formed by plasma deposition. 
     
     
         17 . The gun barrel liner of  claim 16 , wherein the inner layer is formed by re-melting the material of the inner layer. 
     
     
         18 . A method of making a gun barrel liner with rifling, the method comprising:
 depositing material onto a ridged outer surface of the mandrel to form the gun barrel liner, wherein the ridged outer surface corresponds to the rifling;   wherein the depositing includes depositing the materials with different porosity, with inner material of relatively low porosity (less porous) and outer material of relatively high porosity (more porous).   
     
     
         19 . The method of  claim 18 ,
 wherein the depositing includes plasma deposition; and   wherein the depositing includes re-melting the inner material.   
     
     
         20 . The method of  claim 18 , wherein the inner material and the outer material have the same material composition.