Gun barrel and method for producing a gun barrel

Abstract

The invention relates to a gun barrel having a main body (1) with an entry opening and an exit opening, wherein a bore (2) runs from the entry opening to the exit opening, which main body (1) has an inner surface (3), wherein the bore (2) has a diameter of at most 40 mm, and wherein the main body (1) essentially consists of steel, characterized in that a coating (4) is provided at least a part of the surface (3) of the bore (2), in that the coating (4) contains or is a ceramic coating layer (5). The invention also relates to a firearm and to a method.

Description

[0001] 65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT)

[0002] Gun barrel and method for producing a gun barrel

[0003] The invention relates to a gun barrel, a firearm, and a method for producing a gun barrel, as particularly defined by the independent patent claims. Specifically, the invention pertains to the technical field of gun barrels, which have a coating on at least part of its inner surface.

[0004] The manufacturing of coatings inside cavities and on inner surfaces of articles of manufacture is generally of significant industrial relevance. Coatings on such surfaces are often required to improve one or more surface properties, such as wear resistance, fatigue resistance, oxidation resistance, and / or corrosion resistance. Typical applications where enhanced surface properties on internal surfaces are desirable include, for example, pipes, barrels, housings, valves, shock absorbers, hydraulic actuators, forming tools, forming equipment, nozzles, tanks, and heat exchangers.

[0005] Various techniques are known for applying metallic coatings, commonly based on electrochemical processes. For the preparation of non-metallic coatings, alternative coating methods, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), have to be used. However, these methods present specific limitations when applied to an inner surface of hollow articles. In particular, CVD requires high process temperatures that may adversely affect the microstructure of materials such as65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) steel, risking a significant reduction of the mechanical properties of the article.

[0006] Conventional PVD, on the other hand, is a line-of-sight process and therefore cannot readily be used to coat inner surfaces of hollow articles.

[0007] To overcome the line-of-sight limitation of conventional PVD, approaches have been developed involving the confinement and guiding of a PVD plasma into a narrow cavity, thereby enabling coating of the cavity’s inner surface. A successful solution has been described in the published international patent application WO 2022 / 261684 A1 , where an innovative plasma source design was introduced that can be used to coat inner surfaces of hollow articles.

[0008] In the field of gun barrels, it is generally known to provide coatings using materials such as chrome to protect the bore from wear, corrosion, and harsh conditions, increasing its lifespan and improving performance. Coatings provided on the surface of the bore, which inevitably is an inner surface that is not easily accessible for conventional coating equipment, are typically prepared using electrochemical or chemical methods.

[0009] Such methods typically include a number of steps, which makes the coating process cumbersome and expensive. For example, these methods typically require a finishing step, in which the coating surface is polished or treated, such that the surface roughness is kept at a minimum and the performance is increased. The use of electrochemical or chemical methods for coating also involves the possibility that the structural and mechanical properties of the gun barrel’s main body are influenced in the preparation process, for example due to chemical modifications and / or the application of heat, which can adversely affect the overall properties of the gun barrel.

[0010] The chemical and electrochemical methods often include toxic chemicals potentially exposing workers and environment to problematic emissions.

[0011] It is therefore an object of the invention to at least partially overcome one or more of the above-mentioned drawbacks of the prior art.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) The present inventors have now found that it can be desirable to provide a gun barrel, which has a coating on the inner surface of its main body, which coating is preferably prepared using a non-chemical coating process, such as PVD.

[0012] This way, at least some of the main drawbacks of conventional gun barrel coating technologies can be overcome, as PVD relies on highly ionized plasma to deposit coatings and therefore the treatment temperatures can be kept low, and low-roughness surfaces can be created, which do not require a subsequent finishing step.

[0013] Using the non-chemical coating process, it is particularly possible to obtain high-hardness coatings, such as ceramic coatings.

[0014] A “non-chemical coating process” is to be understood as a coating process in which the metal atoms or metal atom fraction contained in the coating material is introduced into the coating process without the use of precursors that require a reaction and / or decomposition to release the metal species for the formation of a coating at the substrate surface.

[0015] Non-chemical coating processes encompass physical application methods in which the deposited metal ratio of the coating material retains substantially the same metal ratio as its source material. However, to form compound coatings like transition metal nitrides the non-metal and / or metalloid fraction of the coating can be introduced as a gaseous phase that reacts with the metal fraction at the substrate surface to form the compound coating. Such coating methods are encompassed by the term “non-chemical coating process”. The weight fraction of the non-metal and / or metalloid element, which comprises the coating, in the gas is 70 wt.-% or higher.

[0016] A specific example of a non-chemical coating process is physical vapor deposition (PVD). It is based in the concept of deposition of a coating material from a vapor phase onto a substrate surface under vacuum or reduced pressure.

[0017] The gun barrel may be a gun barrel for a small-caliber firearm, in which case the bore of the gun barrel has a diameter of at most 40 mm, preferably at most 30 mm, and more preferably at most 20 mm. For the purposes of the present invention, the term65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) “diameter” is to be understood as the largest distance from one side of the bore to the opposite side, measured in a direction orthogonal to the longitudinal extension of the barrel, and particularly at the exit opening of the bore. The diameter of the bore may also be referred to as “caliber”.

[0018] The bore typically runs from an entry opening to an exit opening, which direction defines the direction of longitudinal extension of the bore.

[0019] The gun barrel may be a separate or separable part of a firearm, or it may be an integral part of a firearm. A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual.

[0020] The main body of the gun barrel typically essentially consists of steel.

[0021] The expression “essentially consists of steel” is to be understood as meaning that the bulk material of the component is steel, i.e., an iron-carbon alloy which may contain one or more conventional alloying elements such as chromium, molybdenum, nickel, vanadium, manganese, silicon, or others in amounts typical for commercially available steel grades, together with unavoidable impurities such as sulphur, phosphorus, oxygen, or nitrogen at levels inherent to steel production. The expression “essentially consists of” allows the presence of other materials, such as via surface treatments, platings, or coatings, and of minor amounts of other constituents that do not materially affect the mechanical, thermal, or chemical properties of the gun barrel’s main body. The expression, however, excludes the presence of substantial amounts of other metallic or non-metallic materials which would alter the essential characteristics of the steel.

[0022] The inner surface of the gun barrel may either be a smooth bore or rifled with conventional rifling, characterized by lands and grooves, or polygonal rifling.

[0023] The main body of the gun barrel is typically manufactured from alloy steels selected to provide a combination of high tensile strength, wear resistance, and toughness. Suitable steels include chrome-molybdenum alloy steels such as AISI 4140 (42CrMo4) and AISI 4150 (50CrMo4), which exhibit high hardenability and fatigue resistance. In particular,65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) AISI 4150 is often specified for military-grade gun barrels owing to its increased carbon content and enhanced wear performance. Stainless steels such as 416R and 410 martensitic stainless steel may also be employed. Generally, the choice of steel may be adapted to the intended caliber, operating pressure, and desired service life of the barrel according to the common general knowledge of a skilled person in the relevant art.

[0024] Using the coating of the invention, the bulk properties of the gun barrel’s main body may essentially not be affected. This particularly means that the coating process does not lead to essential alterations in the microstructure and / or the composition of the material of the main body.

[0025] This may mean that the grain size of the material of the main body in any area is essentially the same before and after the coating process.

[0026] Additionally or alternatively, this may mean that the hardness of the material of the main body in any area is essentially the same before and after the coating.

[0027] Additionally or alternatively, this may mean that the coating directly adheres to the material of the main body, without any intermediate layers being present. An intermediate layer in this meaning may be a separate layer or a part of the material of the main body, which has undergone a modifying treatment, such as oxidation.

[0028] For the purposes of the present invention, the grain size of the microstructure may be determined in accordance with ISO 643:2024 using the intercept method. In this method, a polished and appropriately etched metallographic section of the material is prepared to reveal the grain boundaries. Test lines of predetermined length are superimposed on an image of the microstructure, and the number of grain boundary intersections along the test lines, is counted. The test lines may run parallel to the inner surface of the main body and they may be positioned at different depths from the inner surface for comparing the grain size at different depths.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) For the purposes of the present invention, the hardness of the material of the main body may refer to the Vickers micro hardness, determined in accordance with ISO 6507-1 :2018 with a test force of 0.5 kgf (HV0.5) and the hardness of the deposited coating may refer to Indentation Hardness HITC, determined in accordance with ISO 14577-4:2017.

[0029] The coating may consist of one or more layers, wherein the coating at least has one ceramic coating layer. An additional metallic coating layer may be provided, which may particularly be arranged between the inner surface of the main body, and the ceramic coating layer. The metallic coating layer may be directly attached to the material of the main body on one side and to the ceramic coating layer on the other side.

[0030] The ceramic coating layer may also form the complete coating, in which case the ceramic coating layer is directly attached to the material of the main body.

[0031] The ceramic coating layer may comprise or consist of one or more of the following: a metal nitride; a metalloid nitride; a metal carbide; a metalloid carbide; a metal carbonitride; a metalloid carbonitride. These compounds are to be understood as a compound formed between nitrogen and / or carbon and one or more metallic and / or metalloid elements. Suitable elements include, for example, titanium, chromium, zirconium, hafnium, vanadium, niobium, tantalum, aluminium, silicon, boron, molybdenum, tungsten, and mixtures or alloys thereof. The nitride or carbide or carbonitride may be stoichiometric or sub-stoichiometric or over-stoichiometric, wherein an amount of at least 0.5 at.-% nitrogen and / or carbon is preferred, the amount of nitrogen and / or carbon being relative to the total atomic amount of the metal(s) I metalloid(s) in the ceramic coating layer.

[0032] In a specific embodiment, the ceramic coating layer consists or essentially consists of chromium nitride.

[0033] In another specific embodiment, the ceramic coating layer consists or essentially consists of chromium aluminum nitride.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT)

[0034] The metallic coating layer, if present, may comprise or consist of one or more metals.

[0035] In a specific embodiment, the metallic coating layer consists or essentially consists of chromium.

[0036] The gun barrel as disclosed herein may be prepared using an apparatus and / or a method as disclosed in WO 2022 / 261684 A1 , which is incorporated in the present application in its entirety.

[0037] The method of preparing the gun barrel generally may comprise the steps of:

[0038] - generating a plasma,

[0039] - creating and / or providing gaseous species for the coating,

[0040] - condensation of the gaseous species onto the inner surface of the gun barrel’s main body for forming the coating.

[0041] The plasma may be generated by means of electron emission utilizing a plasma source. The gaseous species may be, but are not necessarily, generated by transitioning material from the target of the plasma source into the gas phase by means of the generated plasma. Additional gases may be added.

[0042] In order to coat the inner surface of the gun barrel, the plasma is guided into the bore of the gun barrel’s main body.

[0043] The plasma source typically has an elongate shape and comprises a cathode as well as a target, wherein the target is an electron emission source, and wherein the target is connected to the cathode. The plasma source further comprises a masking, which partially covers the outer surface of the cathode and the target, and which masking is adapted to prevent the formation of plasma on an area covered by the masking during operation of the apparatus, wherein a plasma formation area is provided on the target, which plasma formation area is not covered by the masking.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) The invention particularly relates to a gun barrel having a main body with an entry opening and an exit opening, wherein a bore runs from the entry opening to the exit opening, which main body has an inner surface, wherein the bore preferably has a diameter of at most 40 mm, and wherein the main body essentially consists of steel.

[0044] It is preferably provided that the coating is on at least a part of the surface of the bore, and that the coating contains or is a ceramic coating layer.

[0045] It may be provided that the coating is applied by a non-chemical coating process, which non-chemical coating process preferably is a physical vapor deposition coating process.

[0046] It may be provided that the hardness of the main body, measured at a depth of 0.5 mm from a predetermined point on the inner surface, is at least 20%, preferably at least 30% higher than the hardness of a reference sample, wherein the reference sample is from the same material as the main body and wherein the reference sample has been annealed at a temperature of 900°C for 4 h before cooling to ambient temperature at a cooling rate of at most 1°C / min, wherein the hardness is the Vickers micro hardness HV0.5, determined in accordance with ISO 6507-1:2018.

[0047] It may be provided that the hardness of the surface of the coating is at least 13 GPa, wherein the hardness is the Indentation hardness HITC, determined in accordance with ISO 14577-4:2017.

[0048] It may be provided that the ceramic coating layer of the coating contains at least one metal and / or at least one metalloid, and wherein the ceramic coating layer has a nitrogen content, a carbon content, or a combined content of carbon and nitrogen, of at least 0.5 at.-% based on the total amount of all metals and / or metalloids in the ceramic coating layer (5).

[0049] It may be provided that the thermal conductivity of the coating is less than 30 W*rrr1*K’1, as determined in accordance with ISO 18555:2016 or ISO 24449:2021.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) It may be provided that the thickness of the coating is at most 30 pm, preferably between 1 pm and 15 pm.

[0050] It may be provided that the length of the bore, where the coating is provided, is at least 5 cm, such as at least 50 cm.

[0051] It may be provided that the ceramic coating layer of the coating contains chromium and optionally aluminum.

[0052] It may be provided that the coating apart from the ceramic coating layer has a metallic coating layer, wherein the metallic coating layer is arranged between the ceramic coating layer and the main body.

[0053] The invention particularly also relates to a firearm having a gun barrel has described herein.

[0054] The invention particularly also relates to a method for forming a gun barrel as described herein, wherein the method comprises the following steps:

[0055] - providing a main body of the gun barrel,

[0056] - guiding a plasma into the bore of the main body, wherein the plasma source has an elongate shape and comprises a cathode as well as a target, wherein the target is a electron emission source, and wherein the target is connected to the cathode in an electrically conductive manner, and wherein the plasma source further comprises a masking, which partially covers the outer surface of the cathode and the target, and which masking is adapted to prevent the formation of plasma on an area covered by the masking during operation of the apparatus, wherein a plasma formation area is provided on the target, which plasma formation area is not covered by the masking,

[0057] - generating a plasma by means of electron emission from the cathode and / or target of the plasma source,

[0058] - transitioning material from the target of the plasma source into the gas phase by means of the generated plasma,

[0059] - depositing gaseous material on the inner surface of main body for forming the coating.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) It may be provided that the grain size of the microstructure of the main body after forming the coating, measured at a depth of 0.5 mm and / or 3 mm from a predetermined point on the inner surface, differs by no more than 20%, preferably by no more than 10%, from the grain size of the microstructure of the main body before forming the coating, measured at the same position, wherein the grain size is measured in accordance with ISO 643:2024 using the intercept method, wherein the intercepts run parallel to the surface.

[0060] It may be provided that the hardness of the main body after forming the coating, measured at a depth of 0.5 mm and / or 3 mm from a predetermined point on the inner surface, differs by no more than 10%, preferably by no more than 5%, from the hardness of the main body before forming the coating, measured at the same position, wherein the hardness is the Vickers micro hardness HV0.5, determined in accordance with ISO 6507-1:2018.

[0061] Further and separately disclosed is a gun barrel suitable for large caliber weapons such as artillery weapons, anti-aircraft weapons, tanks, naval guns, with the features of the gun barrel described herein. A gun barrel suitable for large caliber weapons differs from the gun barrel according to the invention in the diameter of the bore. In such gun barrel, the diameter of the bore is at least 40 mm, such as at least 100 mm. A gun barrel suitable for large caliber weapons may have one or more of the features of the inventive gun barrel. Also disclosed is a large caliber weapon with such gun barrel and a method for producing such gun barrel.

[0062] In a large caliber weapon, the thickness of the coating may be up to 500 pm.

[0063] Further features of the present invention can be derived from the claims, the drawings, and the following detailed description of exemplary embodiments according to the present invention.

[0064] In the following, the present invention will be explained in detail with reference to exemplary embodiments of the inventive aspects. The exemplary embodiments are not65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) intended to limit the scope of protection, which is solely defined by the features of the independent claims.

[0065] In the drawings:

[0066] Fig. 1 shows a schematic sectional side view of a part of a gun barrel according to a first embodiment;

[0067] Fig. 2 shows a schematic sectional front view of a the gun barrel according to the first embodiment;

[0068] Fig. 3 shows a schematic sectional front view of a gun barrel according to a second embodiment.

[0069] Unless otherwise noted, the drawings show the following features: main body 1 ; bore 2; inner surface 3 (of the main body 1); coating 4; ceramic coating layer 5; metallic coating layer 6. The drawings are generally not to scale.

[0070] Fig. 1 shows a schematic sectional side view of a part of a gun barrel according to a first embodiment. Fig. 2 shows a schematic sectional front view of that gun barrel.

[0071] The gun barrel is specifically adapted for use in a rifle. The main body 1 is made of AISI 4140 steel, and the bore 2 has a diameter of approx. 7.62 mm.

[0072] The inner surface 3 of the main body 1 is provided with a coating 4, which consists of only one layer, namely the ceramic coating layer 5, which in this embodiment is a chromium nitride layer with at least 30 at.-% nitrogen based on the amount of chromium. The ceramic coating layer 5 has a thickness of approx. 3 pm, an Indentation Hardness HITC, determined in accordance with ISO 14577-4:2017, of approx. 15 GPa, and a thermal conductivity of approx. 5 W*rrr1*K’1, determined in accordance with ISO 18555:2016 or ISO 24449:2021.

[0073] Due to the specific coating process, as described below, the microstructure of the steel of the main body 1 is essentially unaltered by the coating process, meaning that there is no essential difference in grain size, micro hardness, and chemical composition of any region before and after the coating process.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) Additionally, the hardness of the steel of the main body 1 at a distance of 0,5 mm below the coating is at least 30% higher than the hardness of a reference sample of the steel of the main body 1 , wherein the reference sample has been annealed for 4 h at a temperature of 900° under vacuum and cooled to ambient temperature at a rate of at most 1°C / min.

[0074] Fig. 3 shows a schematic sectional front view of a gun barrel according to a second embodiment. This second embodiment is similar to the first embodiment, with the only difference that the coating 4 has two layers, namely the metallic coating layer 6 and the ceramic coating layer 5, wherein the metallic coating layer 6 is sandwiched between the inner surface 3 of the main body 1 and the ceramic coating layer.

[0075] The overall thickness of the coating in this embodiment is approx. 5 pm. The Indentation Hardness HITC, determined in accordance with ISO 14577-4:2017, is approx.

[0076] 16 GPa, and the thermal conductivity is approx. 6 W*rrr1*K’1, determined in accordance with ISO 18555:2016 or ISO 24449:2021.

[0077] The ceramic coating layer 5 is made of the same material as in the first embodiment. The metallic coating layer 6 is a metallic chromium layer.

[0078] The coatings 4 of the first and second embodiment have been prepared as follows, in detail also described in the first embodiment of WO 2022 / 261684 A1 :

[0079] A coating apparatus with a plasma source was used. The plasma source has an essentially tubular, elongate shape and comprises a cathode and a target being connected to the cathode in an electrically conductive manner.

[0080] The cathode and the target are covered by a masking, which is made of electrically non-conductive material. The free end of the plasma source, in particular a part of the target at the free end of the plasma source, is not covered by the masking.

[0081] While the masking serves the purpose of preventing plasma in areas being covered by said masking, plasma can be formed in areas which are not covered by the masking.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) The latter area is therefore referred to as plasma formation area. The target is of tubular shape and the masking partially covers the circumferential outer surface of the plasma source and target.

[0082] The plasma source contains a gas supply channel which allows the process gas to be directly introduced into the created plasma.

[0083] The main body 1 is placed on a fixture inside a vacuum chamber. Then, the gas pressure inside the vacuum chamber is controlled to below 500 Pa.

[0084] The plasma process for treatment of the inner surface 3 of the main body 1 using the plasma source is achieved by electron emission utilizing the plasma source

[0085] while the coating deposition is facilitated by interaction of said electrons with the process gas and transition of target material into the gaseous phase.

[0086] When igniting the plasma, argon gas is introduced into the vacuum chamber at a partial pressure of 8 Pa. The plasma is ignited by applying a voltage of approx. 1000 V at pulsed voltage to the cathode in a first ignition phase. The used frequency of the pulsed voltage is approx. 100 kHz with 50% alternation. For operation, the plasma is sustained by means of a discharge voltage of approx. 120 V with a discharge current of approx.

[0087] 0.6 A.

[0088] The plasma is then moved through the bore 2 of the gun barrel.

[0089] The material of the target is evaporated by means of the plasma and deposited on the inner surface of the main body 1 , thus obtaining the coating 4. The target is made from metallic chromium. In case of preparing the ceramic coating layer 5, additionally nitrogen is introduced via a gas supply channel in order to form CrN.

[0090] The conditions for igniting and sustaining the plasma depend in particular on the material of the target. Proper selection of the condition lies fully within the knowledge of an ordinary skilled person.65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) An anode of the coating apparatus at least partially consumes the electrons which are emitted at the target during the plasma discharge. Using the anode, it is possible to provide additional thermal management for the main body 1 by reducing the electron bombardment on the inner surface of the main body 1. The anode can be realized in a design where it enters the bore 2 from the opening on an opposite side than the plasma source.

Claims

65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) Claims1. A gun barrel having a main body (1 ) with an entry opening and an exit opening, wherein a bore (2) runs from the entry opening to the exit opening, which main body (1 ) has an inner surface (3), wherein the bore (2) has a diameter of at most 40 mm, and wherein the main body (1) essentially consists of steel, characterized in that a coating (4) is provided on at least a part of the surface (3) of the bore (2), and in that the coating (4) contains or is a ceramic coating layer (5).

2. The gun barrel according to claim 1 , wherein the coating (4) is applied by a nonchemical coating process, which non-chemical coating process preferably is a physical vapor deposition coating process.

3. The gun barrel according to claim 1 or 2, wherein the hardness of the main body (1), measured at a depth of 0.5 mm from a predetermined point on the inner surface (3), is at least 20%, preferably at least 30% higher than the hardness of a reference sample, wherein the reference sample is from the same material as the main body (1) and wherein the reference sample has been annealed at a temperature of 900°C for 4 h before cooling to ambient temperature at a cooling rate of at most 1°C / min, wherein the hardness is the Vickers micro hardness HV0.5, determined in accordance with ISO 6507-1:2018.

4. The gun barrel according to any of claims 1 to 3, wherein the hardness of the surface of the coating (4) is at least 13 GPa, wherein the hardness is the Indentation hardness HITC, determined in accordance with ISO 14577-4:2017 .

5. The gun barrel according to any of claims 1 to 4, wherein the ceramic coating layer (5) of the coating (4) contains at least one metal and / or at least one metalloid, and wherein the ceramic coating layer (5) has a nitrogen content, a carbon content, or a combined content of carbon and nitrogen, of at least 0.5 at.-% based on the total amount of all metals and / or metalloids in the ceramic coating layer (5).65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) 6. The gun barrel according to any of claims 1 to 5, wherein the thermal conductivity of the coating (4) is less than 30 W*rrr1*K’1, as determined in accordance with ISO 18555:2016 or ISO 24449:2021.

7. The gun barrel according to any of claims 1 to 6, wherein the thickness of the coating (4) is at most 30 pm, preferably between 1 pm and 15 pm.

8. The gun barrel according to any of claims 1 to 7, wherein the length of the bore (2), where the coating (4) is provided, is at least 5 cm, such as at least 50 cm.

9. The gun barrel according to any of claims 1 to 8, wherein the ceramic coating layer (5) of the coating (4) contains chromium and optionally aluminum.

10. The gun barrel according to any of claims 1 to 9, wherein the coating (4) apart from the ceramic coating layer (5) has a metallic coating layer (6), wherein the metallic coating layer (6) is arranged between the ceramic coating layer (5) and the main body (1).

11. A firearm having a gun barrel according to any of claims 1 to 10.

12. A method for forming a gun barrel according to any of claims 1 to 10, wherein the method comprises the following steps:- providing a main body (1 ) of the gun barrel,- guiding a plasma into the bore (2) of the main body (1 ), wherein the plasma source has an elongate shape and comprises a cathode as well as a target, wherein the target is a electron emission source, and wherein the target is connected to the cathode in an electrically conductive manner, and wherein the plasma source further comprises a masking, which partially covers the outer surface of the cathode and the target, and which masking is adapted to prevent the formation of plasma on an area covered by the masking during operation of the apparatus, wherein a plasma formation area is provided on the target, which plasma formation area is not covered by the masking,65179 / M B / - Plasmateria GmbH, Lembbckgasse 49 / 1 / B / EG, 1230 Wien (AT) - generating a plasma by means of electron emission from the cathode and / or target of the plasma source,- transitioning material from the target of the plasma source into the gas phase by means of the generated plasma,- depositing gaseous material on the inner surface (3) of main body (1 ) for forming the coating (4).

13. The method according to claim 12, wherein the grain size of the microstructure of the main body (1) after forming the coating (4), measured at a depth of 0.5 mm and / or 3 mm from a predetermined point on the inner surface (3), differs by no more than 20%, preferably by no more than 10%, from the grain size of the microstructure of the main body (1 ) before forming the coating (4), measured at the same position, wherein the grain size is measured in accordance with ISO 643:2024 using the intercept method, wherein the intercepts run parallel to the surface (3).

14. The method according to claim 12 or 13, wherein the hardness of the main body (1 ) after forming the coating (4), measured at a depth of 0.5 mm and / or 3 mm from a predetermined point on the inner surface (3), differs by no more than 10%, preferably by no more than 5%, from the hardness of the main body (1 ) before forming the coating (4), measured at the same position, wherein the hardness is the Vickers micro hardness HV0.5, determined in accordance with ISO 6507- 1:2018.

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