Processing of rifled gun barrels from advanced materials

Abstract

Gun barrels made from advanced materials have the potential to provide a significant increase in barrel life as well as a reduction in weight (for advanced ceramic materials) for small caliber systems. The potential use of advanced materials as gun barrels is severely limited due to the difficulty in introducing the rifling pattern on the inner diameter. Most projectiles coming out of the guns are spin stabilized (for aerodynamic flight stability). This spin is imparted by a rifling pattern (lands and grooves) in the inner surface of the gun barrel. The processing of gun barrels made from advanced materials with internal rifling pattern poses a tremendous processing challenge to the materials community. The rifling lands and grooves and desired twist rate coupled with the difficulty of machining some of the advanced materials (ceramics, cermets, hardmetals, etc.) makes the economic manufacturing of such gun barrels extremely difficult. Currently, this form of rifling is achieved by machining in case of metallic gun barrels. The limitation in producing the rifled pattern lies with the conventional processing of complex shaped advanced materials such as ceramics, cermets, or hardmetals. Shaping of these typically requires careful diamond grinding. This grinding process is not only very expensive but it also introduces flaws in case of the brittle ceramics (microcracks). These flaws are detrimental to the performance of these advanced materials as rifled gun barrels. Thus, there is an opportunity and challenge to the materials community to come up with a processing solution that will allow advanced materials such as silicon nitride (Si 3 N 4 ), SiAlON, hardmetals, etc. to be used as gun barrels that have the rifled pattern in the inner diameter. Herein are provided methods and compositions useful to form the rifled gun barrel tubes from advanced materials using little or no machining of the internal rifled geometry.

1 . A powder injection molding (PIM) process for the manufacture of a rifled gun barrel liner comprising an advanced material, said liner having a multiplicity of lands and grooves having a uniform twist, said process comprising feedstock formation to form a feedstock; molding of the feedstock to form a molded feedstock, wherein the molding imparts the multiplicity of lands and grooves; debinding the molded feedstock to form a brown part; and consolidation of the brown part to form the liner. 
     
     
         2 . The process of  claim 1 , wherein the advanced material comprises alumina, hardmetal, silicon nitride, SiAlON, a cermet, zirconia, and/or a superalloy. 
     
     
         3 . The process of  claim 1 , wherein the feedstock comprises alumina, zirconia, SiAlON, silicon nitride, hardmetal, a cermet, a superalloy, silicon and/or carbon. 
     
     
         4 . The process of  claim 1 , wherein the lands and grooves which have a sinusoidal pattern with a uniform and/or a square twist. 
     
     
         5 . The process of  claim 1 , wherein the molding is effected through use of a high-pressure molding machine, a medium-pressure molding machine, and/or a low-pressure molding machine. 
     
     
         6 . The process of  claim 1 , wherein the molding is effected through use of a core rod. 
     
     
         7 . The process of  claim 1 , wherein the feedstock formation comprises mixing a powder of an advanced material or an advanced material precursor with a composition comprising wax, polymer, oil, water, and/or acid. 
     
     
         8 . The process of  claim 1 , wherein the debinding comprises solvent extraction, thermal extraction, wick debinding, catalytic debinding, freeze-drying, and/or supercritical fluid extraction. 
     
     
         9 . The process of  claim 1 , wherein the consolidation comprises pressureless sintering, pressureless liquid-phase sintering, pressure-assisted sintering, and/or containerless hot isostatic processing. 
     
     
         10 . The process of  claim 1 , wherein the rifled gun barrel liner extends throughout the entirety of the length of the breech portion of, but extends less than the entirety of the length of, a gun barrel to which the liner is fitted 
     
     
         11 . The process of  claim 1 , wherein the rifled gun barrel liner comprises a multiplicity of partial gun barrel liners, each of which said partial gun barrel liners lines the entirety of the inner diameter of a portion of, but less than the entirety of the length of, a gun barrel to which the liner is fitted. 
     
     
         12 . The process of  claim 1 , further comprising imparting a compressive loading to the gun barrel liner by constraining the outer diameter of the gun barrel by constraining the outer diameter with a metal tube or a fiber reinforced epoxy winding. 
     
     
         13 . A process for the manufacture of a rifled gun barrel liner comprising an advanced material, said liner having a multiplicity of lands and grooves having a uniform twist, said process comprising feedstock formation; casting of a slurry or a gel, said slurry or gel comprising an advanced material or an advanced material precursor, wherein the casting imparts the multiplicity of lands and grooves; drying/debinding; and consolidation.