Patent Application
20160131461
Broadly, the instant disclosure is directed towards utilizing ammunition cartridge casings. More specifically, the instant disclosure is directed towards different embodiments of utilizing coating systems to protect various case materials (“substrates”) utilized in ammunition casings including aluminum.
Aluminum is utilized as a material in certain ammunition cartridge cases. Aluminum utilization has not been more widespread vs. other materials (such as brass) since a compromised case can react with the hot gases leaking out of the case during a firing event. Such a reaction is known as a “burn-through”. Instances of imperfections in manufacturing a cartridge case can provide a compromised case, where the imperfection can be an initiation site for a burn-through event. Burn through is a failure mode in which high temperature and pressure gas flows (“escapes”) and mix with substrate particles (parts of the case) due to erosion to the case surface from the jet of gas which, in turn, fuels the release of further energy. A burn through event can damage the weapon and/or injure the operator.
With one or more embodiments of the instant disclosure, burn through is reduced, prevented, and/or eliminated for coated cartridge casings utilized in small caliber rounds, even the more powerful firing events for rifle ammunition involving sufficient pressure, time duration, and high temperature and operator exposure that formerly caused aluminum usage to be proscribed as a case material in these applications.
With one or more embodiments of the instant disclosure, burn through is reduced, prevented or eliminated for numerous other applications involving substrate materials that are exposed to high temperature and pressure gas (“plasma”) streams for brief time durations that encompass an entire firing event.
Broadly, the present disclosure relates to protecting surfaces from brief (1-5 millisecond), one-time, high temperature (>2000° C.) exposures which would otherwise damage the surface and the underlying material.
In a short duration event, the transient thermal response of the substrate with its protective coating is the important quantitative information required to compare different candidate materials and engineer the minimum coating thickness for those materials. A thermal model was used to estimate the time until the substrate material exceeds its thermal limit and to engineer the coating thickness for a particular coating and substrate material combination.
In one or more embodiments, of the instant disclosure, the casing system (substrate and coating) is configured to reduce, prevent, and/or eliminate the ignition of the substrate (e.g. aluminum) in a rifle case (e.g. 5.56 mm ammunition case). In some embodiments, the coating comprises a conformal coating.
As used herein, “conformal coating” means: a coating that adheres to a surface. In some embodiments, the conformal coating is configured to spread over the surface to facilitate complete covering and/or encapsulation of the surface (e.g. spreads into the nooks and crannies).
In some embodiments, the coating is configured to promote lubricity with the barrel (e.g. to allow for smooth action within the weapon).
In some embodiments, the coating is configured to promote high temperature resistance with sufficient coating thickness to prevent the substrate material from becoming damaged if it had a flaw (e.g. manufacturing defect, or as the result of handling).
In one aspect, an apparatus is provided, comprising: a substrate configured into a casing, the casing having at least one sidewall such that the casing includes an inner sidewall and an outer sidewall, the casing configured such that it has two opposing ends: a first open, (mouth) end and a second closed, (head) end; a projectile configured to sit within and be retained by the casing and positioned adjacent to the first end (mouth); a propellant, the propellant configured between the projectile and the second end (head end) of the casing, the propellant configured to expand upon a firing event and project the projectile from the casing; and a coating comprising a thermal resistant conformal coating, which can be organic, inorganic, polymer or a combination, which provides a thermal and chemical protecting barrier layer, wherein the coating is configured to cover at least one of the inner sidewall and the outer sidewall, such that at least one side of the substrate is covered by the coating.
In some embodiments, the coating is configured to cover the inner sidewall and outer sidewall of the casing such that the casing is encased within the coating. In some embodiments, the coating is configured to cover the inner sidewall and outer sidewall of the casing such that the casing is entirely encapsulated by the coating layer.
In some embodiments, the casing comprises an ammunition cartridge case.
In some embodiments, the casing comprises a rim-fired ammunition casing.
In some embodiments, the casing comprises a center-fired ammunition casing.
Some non-limiting examples of center-fired ammunition casings are: 5.56 mm NATO; .223 Remington; 9 mm; .40 Caliber S&W; or a .45 ACP.
Some non-limiting examples of high-powered rifles ammunition casings include: 5.56×45 mm NATO, .223 Remington, 30-06 Springfield (7.62×63 mm), 7.62×51 mm NATO, 308 Winchester, .50 BMG (7.72×99 mm).
One or more coating systems of the instant disclosure are configured to be used with aluminum pistol rounds including but not limited to: .45 ACP, .40 Smith & Wesson, 10 mm Auto, .357 Magnum, 38 Special, 9 mm Parabellum, and the .25 Auto. In some embodiments, the casing comprises power capsule (“squib”) for a propellant-operated power tool or other device.
In some embodiments, the substrate is selected from the group consisting of: aluminum, aluminum alloys (e.g. 2xxx, 6xxx, and 7xxx series aluminum alloys, 2024, 6055, 7075, 7085), magnesium, titanium, steel, plastic, and polymers.
In some embodiments, the substrate comprises a pipe (e.g. mining pipe, chemical pipe).
In some embodiments, the substrate comprises a power capsule (“squib”) for a propellant-operated device such as: an occupant-restraint air bag assembly in an automotive vehicle.
In some embodiments the substrate comprises a surface exposed to a brief (1-3 millisecond), one-time thermal event involving a gas jet at a temperature of at least 2500° C.
In one aspect, an apparatus is provided, comprising: a substrate configured into a casing, the casing having at least one sidewall such that the casing includes an inner sidewall and an outer sidewall, the casing configured such that it has two opposing ends: a first end and a second end; a projectile configured to sit within and be retained by the casing and positioned adjacent to the first end; a propellant, the propellant configured between the projectile and the second end of the casing, the propellant configured to expand upon a firing event and project the projectile from the casing; and a coating comprising a fluoropolymer layer having a particulate boron nitride therein (e.g. dispersed therein), wherein the coating is configured to cover at least one of the inner sidewall and the outer sidewall, such that at least one side of the substrate is covered by the coating.
In one aspect, an apparatus is provided, comprising: an ammunition cartridge casing comprising a substrate configured to retain a projectile and a propellant, wherein the ammunition cartridge casing is configured with a coating thereon, wherein the coating includes: a conformal coating portion and an additive configured to be dispersed within the conformal coating portion.
In some embodiments, the conformal coating portion is configured to cover the substrate (e.g. completely encase the substrate).
In some embodiments, the conformal coating comprises a fluoropolymer.
In some embodiments, the additive comprises a ceramic additive.
In some embodiments, the ceramic additive is selected from the group consisting of: alumina, boron nitride, titania, and combinations thereof.
In some embodiments, the additive is present in a range of: at least 5 wt. % to not greater than 70 wt. %. In some embodiments, the additive is present in a range of: at least 15 wt. % to not greater than 50 wt. %. In some embodiments, the additive is present in a range of: at least 30 wt. % to not greater than 50 wt. %. In some embodiments, the additive is present in a range of: at least 35 wt. % to not greater than 45 wt. %.
In some embodiments, the additive is present in a content of: at least 5 wt. %; at least 10 wt. %; at least 15 wt. %; at least 20 wt. %; at least 25 wt. %; at least 30 wt. %; at least 35 wt. %; at least 40 wt. %; at least 45 wt. %; at least 50 wt. %; at least 55 wt. %; at least 60 wt. %; at least 65 wt. %; or at least 75 wt. %.
In some embodiments, the additive is present in a content of: not greater than 5 wt. %; not greater than 10 wt. %; not greater than 15 wt. %; not greater than 20 wt. %; not greater than 25 wt. %; not greater than 30 wt. %; not greater than 35 wt. %; not greater than 40 wt. %; not greater than 45 wt. %; not greater than 50 wt. %; not greater than 55 wt. %; not greater than 60 wt. %; not greater than 65 wt. %; or not greater than 75 wt. %.
In some embodiments, the casing (e.g. ammunition cartridge with coating) is capable of withstanding pressure during a firing event yielding a pressure of at least 40 ksi.
In some embodiments, the casing (e.g. ammunition cartridge with coating) is capable of withstanding a firing event duration of at least 2.2 ms.
In some embodiments, the ammunition cartridge casing is capable of withstanding a temperature during a firing event of not greater than 3000° C.
In some embodiments, the coating is a sacrificial coating (i.e. is lost/burned off as a result of the firing event).
In some embodiments, the coating is configured on the outside surface of the case.
In some embodiments, the coating is configured on the inside surface of the case.
In some embodiments, the coating is configured to encase the substrate (e.g. completely cover and surround the inside, outside, and upper lip/opening, along with base of the case). In some embodiments, the coating is configured to entirely encapsulated by the coating layer.
In some embodiments, the additive comprises a particulate material. In some embodiments, the particulate material comprises a ceramic particulate material.
In some embodiments, the additive comprises a particulate refractory material (e.g. typically utilizable in a high temperature application). In some embodiments, the additive comprises refractory materials having low thermal diffusivity and high temperature and chemical corrosion resistance.
In some embodiments, the additive is selected from the group: alumina, titania, zirconia, boron nitride, cubic boron nitride, hexagonal boron nitride, boron nitride polymorphs, silica (SiO2), silicon carbide (SiC), chromia (Cr2O3), tungsten carbide, halfnium carbide, tantalum carbide, tantalum-halfnium carbide, and combinations thereof.
In some embodiments, the additive comprises uniformly sized granules.
In some embodiments, the additive comprises non-uniformly sized granules.
In some embodiments, the coating thickness ranges from 0.25 mil to 2.0 mil thick on a single substrate (casing). In some embodiments, the average coating thickness is between 0.25 mil and 2.0 mil.
In some embodiments, the coating thickness ranges from 1.5 mil to 2.0 mil thick.
In some embodiments, the average coating thickness is: at least 0.25 mil; at least 0.5; at least 0.75 mil; at least 1 mil; at least 1.25 mil; at least 1.5 mil; at least 1.75 mil; at least 1.75 mil thick; or at least 2 mil thick.
In some embodiments, the coating thickness is: not greater than 0.25 mil; not greater than 0.5 mil; not greater than 0.75 mil; not greater than 1 mil; not greater than 1.25 mil; not greater than 1.5 mil; not greater than 1.75 mil; not greater than 1.75 mil thick; or not greater than 2 mil thick.
In some embodiments, the additive comprises a spherical shape (e.g. particulate or powder).
In some embodiments, the additive comprises a plate-like shape (e.g. particulate or powder).
In some embodiments, the additive comprises a polygonal cube shape (particulate or powder).
In some embodiments, the additive comprises a prismatic shape (e.g. with an aspect ratio of approximately 1.0), possibly in particulate or powder forms.
In some embodiments, the additive comprises a whisker shape (e.g. thin-rod shaped, fibers, or particulate form).
In some embodiments, the additive comprises a discoidal shape (e.g. circular flat shape).
In some embodiments, as qualified or quantified via visual observation, the casing does not exhibit a burn through event.
In some embodiments, as qualified or quantified via visual observation, the casing does not exhibit significant erosion of the substrate, and therefore does not add the eroded material to the gas stream as combustible material.
In some embodiments, as qualified or quantified via visual observation, the casing does not exhibit melting.
In some embodiments, the coating is configured to insulate the substrate from the heat and pressure of the firing event.
In some embodiments, the coating is configured to isolate the substrate from contact with the gas released during the firing event (i.e. gas caused by ignition of propellant).
In some embodiments, the coating comprises an organic conformal coating.
In some embodiments, the coating comprises a fluoropolymer.
In some embodiments, the coating comprises a fluoropolymer, a solvent/carrier liquid, and at least one additive.
In one aspect, an apparatus is provided, comprising: a cartridge case comprising a substrate (e.g. Al, Ti, brass, steel, plastic), the cartridge case having: a base, a perimetrical sidewall configured to surround the base and extend upward from the base, and an open, upper end, and a coating on the base and the perimetrical sidewall of the cartridge case; wherein, via the coating, the cartridge case does not exhibit burn-through during a firing event that has a duration of greater than two milliseconds, where the firing event produces a gas having pressure of at least 40 ksi and a temperature not greater than 3000° C.
In one aspect, a method is provided comprising: forming a cartridge casing from a substrate material to provide a body having at least one sidewall, the cartridge casing having a first end and a second end, wherein the cartridge casing is configured to retain a projectile and a propellant; coating a cartridge casing with a layer of organic conformal coating including a ceramic particulate dispersed therein; drying (curing) the coating to remove a solvent from the coating and set the coating onto the surface of the substrate (e.g. inner sidewall and/or outer sidewall); positioning the propellant and the projectile within the casing; forming an ammunition cartridge.
In some embodiments, coating (e.g. the step of positioning/depositing the coating on the substrate/case) comprises: spraying, dipping, brushing/painting, rolling, and combinations thereof.
In some embodiments, the method comprises cleaning the surface of the substrate prior to coating the substrate with an organic conformal coating (i.e.: fluoropolymer).
In some embodiments, the method comprises deoxidizing the surface of the substrate (e.g. when the substrate is an aluminum alloy) prior to coating the substrate with an organic conformal coating.
In some embodiments, the coating including a ceramic additive, comprises an orientation of the ceramic additive particles within the coating, wherein the orientation is configured to impart thermal protection and/or insulation to the substrate. In some embodiments, the ceramic additive (e.g. hBN) is plate-like (e.g. flat).
In some embodiments, the coating comprises an organic conformal coating comprising a hexagonal boron nitride with a flat orientation (e.g. 1106 hBN) against the substrate surface.
In some embodiments, the coating comprising a ceramic additive is configured to lie in a flat orientation, parallel to the surface of the case. In some embodiments, hexagonal boron nitride (PUHP 1106) is configured in a flat plate configuration, such that it lies in a substantially flat configuration, such that the plates are configured parallel to the surface of the substrate.
Various ones of the inventive aspects noted hereinabove may be combined to yield coating systems that provide at least one of: insulation of the underlying substrate from surrounding pressure and temperature gradients and isolation of the underlying substrate from direct contact with the hot gases associated with a high temperature/high pressure event (e.g. firing event).
These and other aspects, advantages, and novel features of the invention are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing the invention.
Referring to
In the adjusted weight loss charts (i.e.
Referring to
Reference will now be made in detail to the accompanying drawings and the experiments performed to support the various embodiments herein, which at least assist in illustrating various pertinent embodiments of the present invention.
For the .40 Caliber firing trials, undamaged casings and intentionally damaged casings were coated and fired. The intentionally damaged casings were included in the firing trials to confirm what, if any, protective impact the various coating systems would provide casings, in the event of a flaw in the wall of a casing permitting the leakage of propellant gas.
In order to simulate such manufacturing defects, several sizes of round holes were drilled into the sidewalls of cases; a small, medium, or large hole. The cartridges had either: no hole (N)—no damage; a small hole (0.015 inch diameter); a medium hole (0.0625 inch diameter); or a large hole (0.080 inch diameter) in the casing, along with a machine groove in-line with the hole, to facilitate leakage of gases past the case sidewall.
The holes and grooves for the .40 caliber cases were machined into the cartridges prior to coating.
Control 1: Bare Case
For these cases, no surface preparation was completed. The casings were fired as-received.
Control 2: Type III Anodized Cases:
For the Type III anodized cases, the cartridges were anodized in sulfuric acid at 20% by weight, 50° F., with a current density of 36 amperes per square foot (asf) for 40 minutes. Oxide thickness was 0.3 mil. The anodized surface was sealed in Sealing Salt AS (nickel acetate solution)) @200° F. for 10 minutes.
System A: FP Over Type III with Alternate Sealant
The FP was applied to anodized (unsealed) cases that had been placed dry in a vacuum bag until FP was ready to be applied. The firing trial determined that this coating did little to nothing to protect the case from burn through, as compared to the Control—Type III Anodic coating (only).
To apply a Type III anodizing layer to the cases, the cases were anodized in sulfuric acid at 20% by weight, 50° F., 36asf for 40 minutes. Oxide thickness was 0.3 mil. The anodized surface was unsealed with nickel acetate sealant.
A fluropolymer coating (PPG 1HC5697 Durabrite C high gloss clear Fluoropolymer) was applied to over the surface of the Type III anodized case. To apply the coating, the cases were hand-coated twice with an 80/20 (by volume) mixture consisting of fluoropolymer coating and Methyl Isobutylketone (MIBK). The coated case was flashed off for three minutes in between applications and prior to oven cure. The coating was cured for 8 minutes in an electric oven set to 470° F., with a PMT of 454° F. After it was confirmed by visual inspection that the coating had not covered the groove, fluoropolymer coating was applied to the hole and in-line groove with a paint brush and the casing was cured a second time.
To apply a Type III anodizing layer to the cases, the cases were anodized in sulfuric acid at 20% by weight, 50° F., 36asf for 40 minutes. Oxide thickness was 0.3 mil. The anodized surface was sealed in Sealing Salt AS (nickel base) @200° F. for 10 minutes.
A fluropolymer coating (PPG 1HC5697 Durabrite C high gloss clear Fluoropolymer) was applied to over the surface of the Type III anodized case. To apply the coating, the cases were hand-coated (dipped) twice with an 80/20 mixture consisting of 80% fluoropolymer coating and 20% methyl isobutylketone (MIBK). The coated case was flashed off for three minutes in between applications and prior to oven cure. The coating was cured for 8 minutes in an electric oven set to 470° F., with a PMT of 459° F. After it was confirmed by visual inspection that the coating had not covered the groove, fluoropolymer coating was applied to the hole and in-line groove with a paint brush and the casing was cured a second time.
System C: Fluropolymer Coating Mixed with Particulate at 35 wt. % (1106 hBN)
To prepare the surface of the aluminum case, the case was cleaned and deoxidized. A cleanser was applied to the casing (A31K Alkaline cleaner) 2.5 minutes at 140° F., followed by a rinse in tap water, then a spray of DI water. To deoxidize the surface, the casing underwent an Anodal® LFN for 2 minutes at room temperature (74°), followed by a tap water rinse and DI water spray.
To a glass jar with glass beads, 19.82 grams of fluoropolymer resin (65% by weight) and 6.94 grams of boron nitride solids (35% by weight) (hBN, PUHP 1106, Saint Gobain) were added. The jar with beads, fluoropolymer and hBN was inserted onto a paint shaker, which was operated for one hour in order to disperse the hBN powder into the fluropolymer coating. Once the mixing was completed, the mixture was further reduced with solvent (MIBK) for coating application.
To apply the fluoropolymer coating, a mixture was prepared consisting of (by volume) of 45 mL fluoropolymer coating (PPG 1HC5697 Lot#19474 Durabrite C high gloss clear fluoropolymer) and 20 mL methyl isobutylketone (MIBK). Then, the casing was hand-dipped and cured. To cure the coating, the coated cases were heated in an electric oven set to 460° F. for a period of 2.5 minutes, with a PMT range from 425° F. to 430° F. Upon visual observation, no issues were noticed during application of the coatings.
System D: Fluropolymer Coating with Particulate 1 (hBN=PUHP 500) Over Bare Case
To prepare the surface of the aluminum case, the case was cleaned and deoxidized. A cleanser was applied to the casing (A31K Alkaline cleaner) 2.5 minutes at 140° F., followed by a rinse in tap water, then a spray of DI water. To deoxidize the surface, the casing underwent an Anodal® LFN for 2 minutes at room temperature (74°), followed by a tap water rinse and DI water spray.
To a glass jar with glass beads, 19.82 grams of fluoropolymer resin and 6.94 grams of boron nitride solids (hBN, PUHP 500, Saint Gobain) were added. The jar with beads, fluoropolymer and hBN was inserted onto a paint shaker, which was operated for one hour in order to disperse the hBN powder into the fluropolymer coating. Once the mixing was completed, the mixture was further reduced with solvent (MIBK) for coating application.
To apply the fluoropolymer/hBN coating, a mixture (by volume) of 45/20 mLs of fluoropolymer coating (PPG 1HC5697 Lot#19474 Durabrite C high gloss clear Fluoropolymer having hBN therein) to methyl isobutylketone (MIBK) was prepared. Then, the casing was hand-dipped and cured. To cure the coating, the coated cases were heated in an electric oven set to 460° F. for a period of 2.5 minutes, with a PMT range from 425° F. to 430° F. Upon visual observation, no issues were noticed during application of the coatings.
System E: Fluropolymer Coating with Particulate 2 (hBN=LEAU 500) Over Bare Case
To prepare the surface of the aluminum case, the case was cleaned and deoxidized. A cleanser was applied to the casing (A31K Alkaline cleaner) 2.5 minutes at 140° F., followed by a rinse in tap water, then a spray of DI water. To deoxidize the surface, the casing underwent an Anodal® LFN for 2 minutes at room temperature (74°), followed by a tap water rinse and DI water spray.
Measured out 19.82 grams of fluoropolymer resin and 6.94 grams of boron nitride solids (hBN, LEAU 500, Saint Gobain) and placed in a glass jar with glass beads. The jar with beads, fluoropolymer and hBN was inserted onto a paint shaker, which was operated for one hour in order to disperse the hBN powder into the fluropolymer coating. Once the mixing was completed, the mixture was further reduced with solvent (MIBK) for coating application.
To apply the fluoropolymer/hBN coating, a mixture (by volume) of 45/20 mLs of fluoropolymer coating (PPG 1HC5697 Lot#19474 Durabrite C high gloss clear Fluoropolymer having hBN therein) to methyl isobutylketone (MIBK) was prepared. Then, the casing was hand-dipped and cured. To cure the coating, the coated cases were heated in an electric oven set to 460° F. for a period of 2.5 minutes, with a PMT range from 425° F. to 430° F. Upon visual observation, no issues were noticed during application of the coatings.
System F: Silicone Coating Over Type III with Standard Sealant
To apply a Type III anodizing layer to the cases, the cases were anodized in sulfuric acid at 20% by weight, 50° F., 36asf for 40 minutes. Oxide thickness was 0.3 mil. The anodized surface was sealed in Sealing Salt AS (nickel base) @200° F. for 10 minutes.
A silicone coating (Dow Corning 1-2577 clear RTV) was applied over the surface of the Type III anodized case. To apply the coating, the cases were hand-coated (dipped) twice with an 1/1 mixture consisting of silicone coating (Dow Corning 1-2577 clear RTV)/Methyl Ethyl Ketone (MEK) and flashed off for three minutes in between applications and prior to oven cure. To cure the coating, the coated cartridges were cured for 10 minutes in an electric oven set at 180° F.
It was observed that the silicone coatings (even reduced with solvent) would not conform over the hole and the in-line groove with the dip method. (Hand-dipping a cartridge into the as-received coating (undiluted with solvent) yielded the same result). A paint brush was utilized to apply the coating over the hole and in-line groove.
This coating was applied by General Magnaplate (Linden, N.J.).
System K: Fluropolymer Coating with Particulate 0 at 45 wt. % (hBN PUHP1106)
System K is similar to System C (.40 caliber system), but utilizes a larger wt. % of ceramic particulate than System C (45 wt. % vs. 35 wt. %).
For each shot completed in the firing trials, each case was visually inspected to observe the coating and uniformity of the coating. After firing, each case was visually observed for burn through. Weight loss was calculated, where weight loss can be a factor in identifying a burn through event. However, where the coating is sacrificial, weight loss is expected as the coating and/or coating constituents come off during the firing event. For each shot, metrics were collected on the firing event to confirm that the fired shot was a good shot/true shot. The firing event data collected for each shot included: (a) peak pressure; (b) time to peak pressure; and (c) velocity of shot. In some instances, firing trials having bad transducer readings were confirmed to be good shots by the shot velocity measurement. All shots in both the .40 Caliber firing trials resulted in good shots.
The following observations were made in view of the data obtained from the firing trails. It was observed that plain fluoropolymer coating over bare aluminum was an improvement over bare aluminum casing (control 1).
It was observed that, during firing trials, the silicone coating became detached from the case interiors when fired and was deposited by the propellant gases onto the barrel of the firearm. This result was deemed unacceptable from a practical (barrel fouling) standpoint and not pursued further. There was no observable burn through even in the large hole, “damaged” cases, but the barrel of the .40 caliber gun was clogged. It is possible, with tweaking of the formulation or application technique, that a silicone coating could be utilized, given the success of the coating in reducing, preventing, and/or eliminating burn-through.
In addition to completing weight loss calculations (to understand whether and to what extent burn through may have occurred), visual observations were also completed. Without being bound by a particular mechanism or theory, weight loss could be attributed to the coating burning off, where loss of the coating could result in protection of the underlying substrate during a firing event (e.g. in the case of a “sacrificial coating”).
Thus, the effectiveness of the coating at protecting the aluminum substrate can be observed in images of the case after the firing event occurred. A large amount of material loss is observable when melting occurs during the firing of the ammunition. When the coating is effective discoloration occurs, but the hole is still near its original dimension and shape and the case can be seen to be intact.
In order to approximate a standardized evaluation of whether and to what extent a “burn through” event occurred in fired cases, a team of seven individuals was assembled. The team included three individuals with backgrounds in coating chemistry, three individuals with engineering backgrounds, and two metallurgists. Each individual visually observed the fired cases and ranked the cases in an order of “best” to “worst” appearance. Subsequently, each of the coating systems assigned a letter grade, which averaged the letter grades of the team members regarding visually observed level/extent of “burn through” events. The letter grades for each of the coating systems is set out below for the two controls and for four coating systems. A letter grade of A denotes little to no burn-through, while a letter grade of C denotes a large amount of/evident burn-through, as evaluated via visual observation. A letter grade of B denotes some burn-through, though less compared to a letter grade of “C” and more as compared to a letter grade of “B”.
The same preps for this trial for the various controls and coating systems were the same as set out above, with the exception that the fluoropolymer with particulate 0 included the particulate at 45 wt %).
Control 1: Bare Case
For these cases, no surface preparation was completed. The casings were fired as-received.
Control 2: Type III Anodized Cases:
For the Type III anodized cases, the cartridges were anodized in sulfuric acid at 20% by weight, 50° F., 36asf for 40 minutes. Oxide thickness was 0.7 mil. The anodized surface was sealed in nickel acetate sealing salt AS @200° F. for 10 minutes.
System K:
To prepare the surface of the aluminum case, the case was cleaned and deoxidized. A cleanser was applied to the casing (A31K Alkaline cleaner) 2.5 minutes at 140° F., followed by a rinse in tap water, then a spray of DI water. To deoxidize the surface, the casing underwent an Anodal® LFN for 2 minutes at room temperature (74°), followed by a tap water rinse and DI water spray.
To a glass jar with glass beads, 19.82 grams of fluoropolymer resin and 8.92 grams of boron nitride solids (hBN, PUHP 1106, Saint Gobain) were added. The jar with beads, fluoropolymer and hBN was inserted onto a paint shaker, which was operated for one hour in order to disperse the hBN powder into the fluropolymer coating. Once the mixing was completed, the mixture was further reduced with solvent (MIBK) for coating application.
To apply the fluoropolymer coating, a mixture was prepared consisting of (by volume) of 45 mL fluoropolymer coating (PPG 1HC5697 Lot#19474 Durabrite C high gloss clear Fluoropolymer) and 20 mL methyl isobutylketone (MIBK). Then, the casing was hand-dipped and cured. To cure the coating, the coated cases were heated in an electric oven set to 460° F. for a period of 2.5 minutes, with a PMT range from 425° F. to 430° F. Upon visual observation, no issues were noticed during application of the coatings.
For the 5.56 mm firing trials, undamaged casings and intentionally damaged casings were coated and fired. The intentionally damaged casings were included in the firing trials to confirm what, if any, protective impact the various coating systems would provide casings, in the event of a small, medium, or large hole in the casing (attributed to a manufacturing defect). The cartridges had no hole (N)—no damage; a small hole (0.025 inch diameter); or a large hole (0.063 inch diameter) in the casing, along with a machine groove in-line with the hole.
For each shot completed in the firing trials, each case was visually inspected to observe the coating and uniformity of the coating. After firing, each case was visually observed for burn through. Weight loss was calculated, where weight loss can be a factor in identifying a burn through event. However, where the coating is sacrificial, weight loss is expected as the coating and/or coating constituents come off during the firing event. For each shot, metrics were collected on the firing event to confirm that the fired shot was a good shot/true shot. The firing event data collected for each shot included: (a) peak pressure; (b) time to peak pressure; and (c) velocity of shot. In some instances, firing trials having bad transducer readings were confirmed to be good shots by the shot velocity measurement. All shots in both the .40 Caliber firing trials and the 5.56 firing trial resulted in good shots.
Without being bound by a particular mechanism or theory, it is believed that as the ceramic additive (e.g. hBN) has a higher melting point than the conformal coating (fluoropolymer coating) the additive is configured to remain intact at a higher temperature (e.g. firing event) and/or sublimate at high temperatures to remove heat of condensation in the firing zone (e.g. within the chamber) to confer a thermal protection benefit to the underlying substrate.
Without being bound by a particular mechanism or theory, in this kind of mixture (i.e. coating with lower melting point and ceramic additive with higher melting point), the benefits of the added ceramic are believed to be conferred to the mixture in a manner akin to a “mixture rule”, where the bulk properties like melting point, thermal conductivity, emissivity, etc., are a combination of these properties of the base coating (matrix) and of the particle, more or less in proportion to the relative amounts of each component (e.g. and, may be generally isotropic and non-directionally oriented or randomly and non-directionally aligned). For example, hBN has a melting temperature at approximately 3000° C., depending on pressure. At standard atmospheric pressure, it sublimates at a temperature of 2973° C. (5383° F.). At elevated pressures of 6 GPa (870226 psi), hBN melts at 3227° C. (5840° F.).
Without being bound by a particular mechanism or theory, it is believed that hBN's ability (in certain forms) to lay in a substantially flat configuration along the surface of the substrate, such that the plates are configured in a substantially parallel direction to the surface of the substrate is believed to provide the least quantity of heat conduction into the substrate (e.g. heat from the gas stream) as compared to other configurations/alignments.
Without being bound by a particular mechanism or theory, it is believed that the alignment configuration of the ceramic additives (e.g. hBN in plate-like configuration) is believed to increase the amount of thermal protection (i.e. insulation) imparted by the coating on the substrate, as compared to amount of thermal protection imparted in a coating having ceramic additives in a randomly oriented plate/flake-like configuration.
In order to evaluate the effectiveness of hexagonal boron nitride as a constituent to the cartridge casings, panel tests were completed, in which hBN was added to the fluoropolymer resin solids (hBN at 35 wt % of the FP resin solids). The ability to mix hBN into the coatings was evaluated, as well as application over aluminum panels (only surface-cleaned). The coated panel specimens were evaluated for coating uniformity using SEM, pencil hardness, and abrasion resistance tests. For Trials 1-6 set out below, each AA 6061 panel was cleaned prior to coating application.
For Trial #1, the coating was an 80/20 mix by volume of Fluoropolymer coating (PPG 1HC5697Durabrite C high gloss clear Fluoropolymer) to MIBK. A vortex mixer was utilized to mix the boron nitride powder into the coating. The 6061 panel was hand-dipped once and flashed off for one minute prior to oven cure. Cure was completed in an electric oven set at 390° F. for 2 minutes.
For Trial #2, the coating was 4.60 grams of hBN powder (PUHP500, Saint Gobain) mixed into 30mLs coating (13.214 grams of fluoropolymer resin solids) coating/7.5 mLs MIBK. A vortex mixer was utilized to mix the boron nitride powder into the coating. The 6061 panel was hand-dipped once and flashed off for one minute prior to oven cure. Cure was completed in an electric oven set at 390° F. for 2 minutes.
For Trial #3, the coating was 4.60 grams hBN powder (PUHP1106, Saint Gobain) mixed into 30 mls (13.214 grams of fluoropolymer resin solids)] coating/7.5 mL MIBK. A vortex mixer was utilized to mix the boron nitride powder into the coating. The 6061 panel was hand-dipped once and flashed off for one minute prior to oven cure. Cure was completed in an electric oven set at 390° F. for 2 minutes.
For Trial #4, the coating was 4.60 grams of hBN powder (PEG Dimethicone Treaded LEAU500, Saint Gobain) mixed into 30 mLs coating (13.214 grams of fluoropolymer resin solids)/7.5 mLs MIBK. A vortex mixer was utilized to mix the boron nitride powder into the coating. The 6061 panel was hand-dipped once and flashed off for one minute prior to oven cure. Cure was completed in an electric oven set at 390° F. for 2 minutes.
For Trial #5, the coating was a combination of fluoropolymer coating (PPG 1HC5697, Durabrite C high gloss clear Fluoropolymer)/Silicone coating (Dow Corning 1-2577 clear RTV)/MIBK in the ratio of 30/5/25 mLs. A vortex mixer was utilized to mix the boron nitride powder into the coating. The 6061 panel was hand-dipped once and flashed off for one minute prior to oven cure. Cure was completed in an electric oven set at 390° F. for 2 minutes.
For Trial #6, the coating was 4.60 grams of hBN powder (PEG Dimethicone Treaded LEAU500, Saint Gobain) mixed into PPG/Dow/MIBK 30/5/25 mLs, by volume. A vortex mixer was utilized to mix the boron nitride powder into the coating. The 6061 panel was hand-dipped once and flashed off for one minute prior to oven cure. Cure was completed in an electric oven set at 390° F. for 2 minutes, and after cure, the coating was inspected and confirmed.
Scratch Resistance Tests were completed in accordance with general industry practices (using a taber linear-abrasion) and test results are depicted in the table below. For each scratch resistance test, a single 2 inch stroke was done (per weight) and evaluated with copper sulfate for coating break through. An acidified copper sulfate was completed on each sample for 5 minutes to verify break through. It was observed that break through diminished as the coating weight increased vs. different loading. It was observed that the coating with silicone added in (silicone+fluoropolymer) had less scratch resistance than the fluoropolymer coating. It was observed that the hBN additive of LEAU 500 did not appear to reduce scratch resistance as compared to no additive. It was observed that both coatings with the PUHP500 & LEAU500 hBN additives provided roughly equivalent scratch resistance as compared to the coating of Fluoropolymer (without hBN). It was observed that the coating with hBN additive PUHP1106 started to show coating break-through at 800 grams of weight.
Coefficient of Friction (CoF) tests were completed on four coating systems and a bare aluminum surface (control). The samples were tested in the rolling direction with a load of 1000 grams. The speed was set at 20% of maximum and the bridge amplifier with a 100% load at full scale. The paper speed setting is 5 centimeters per second.
A one-dimensional thermal model was created in order to predict/project the ability of coatings to survive a firing event. Variables including: coating thickness, coating components, metal substrate, etc. were incorporated into a mathematical model and graphs for various coating systems were plotted, in temperature vs. time according to the firing event's predicted thermal event and firing duration. The goal was for the coating system to protect the underlying metal (aluminum substrate) for a long enough duration and from the full thermal event such that the coating system imparted some protection/barrier to the underlying substrate material during the firing event (e.g. to prevent degradation/a burn through event, in the case of certain substrate materials).
Regarding the simulation, without being bound by any particular mechanism or theory, the flow of propellant gases is estimated using compressible gas flow theory, with the assumption that the flow of gas is a choked flow of propellant gases through the hole. This theory determines the gas properties along the length of the hole: temperature, pressure, density, and velocity. Convective and radiation heat transfer are then estimated using the flow conditions within the hole.
Without being bound by any particular mechanism or theory, it is believed that radiation heat transfer is insignificant as compared to convective heat transfer, and it is possible to estimate the heat transfer from the propellant gases in the drilled hole experiment from the chamber conditions: temperature, pressure, and gas composition.
During the firing event for a 5.56 mm case, the case pressure rises from atmospheric pressure to its maximum pressure 0.7 ms after ignition, then the case pressure decreases to atmospheric pressure 2.2 ms after ignition. The pressure-time trajectory is known, and the peak pressure of the case may be in the range from 50000 psi to 70000 psi.
Published heat transfer estimates were coupled with a one-dimensional computational heat conduction model and compared with published test results comparing brass to anodized aluminum to bar aluminum cartridge cases (in order to establish validity of the model with actual test data).
Without being bound by a particular mechanism or theory, the model calculates the transient temperature response within the coating and case material, which is used to determine the time for the case to heat and begin to melt during a firing event. Results from the model can be calibrated to test data and used to compare different case materials, coating materials and coating thicknesses, and predict the success of other case materials, coating materials and thicknesses.
The table below compares the model prediction with the test observations (e.g. depicted in
The published data from the firing trial suggests there is a threshold between 0.50 ms and 0.63 ms, where case melting increases dramatically.
In the table below, the published test observations are compared with the predictions from the thermal model. As depicted below, shorter time to initiate melting corresponds to case melting, and longer time to initiate melting corresponds to the case being intact after the drilled hole test.
The model was used to identify alloys, coating materials and their thickness that would prevent melting to the same capacity as bare brass.
In some embodiments, the coating comprises a thermal diffusivity of not greater than 5×10−6 m2/s. In some embodiments the coating comprises a maximum temperature of not greater than 2000K.
Without being bound by a particular mechanism or theory, although the adiabatic flame temperature for the propellant gases, typically 3000 K, may be substantially high than the maximum temperature of the coating, it is believed that the duration of heat transfer (during the firing event) is not long enough for the temperature of the coating to heat beyond its upper limit.
While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.
An apparatus, comprising: a substrate configured into a casing, the casing having at least one sidewall such that the casing includes an inner sidewall and an outer sidewall, the casing configured such that it has two opposing ends: a first end and a second end;
a projectile configured to sit within and be retained by the casing and positioned adjacent to the first end; a propellant, the propellant configured between the projectile and the second end of the casing, the propellant configured to expand upon a firing event and project the projectile from the casing; and a coating comprising a conformal coating layer having a particulate boron nitride [dispersed] therein, wherein the coating is configured to cover at least one of the inner sidewall and the outer sidewall, such that at least one side of the substrate is covered by the coating.
In some embodiments, the coating is configured cover the inner sidewall and outer sidewall of the casing such that the casing is encased within the coating.
In some embodiments, the casing comprising an ammunition casing
In some embodiments, the casing comprises an ammunition casing of: 5.56 mm NATO; .223 Remington; 9 mm; .40 Caliber S&W; or a .45 ACP.
In some embodiments, the casing comprising a cartridge for squib for a power tool.
In some embodiments, the substrate is selected from the group consisting of: aluminum, aluminum alloys (e.g. 2xxx, 6xxx, and 7xxx series aluminum alloys, 2024, 6055, 7075, 7085), magnesium, titanium, steel, plastic, and polymers.
In some embodiments, the substrate comprises a pipe (e.g. mining pipe, chemical pipe).
In some embodiments, the substrate comprises an air bags assembly.
An apparatus, comprising: a substrate configured into a casing, the casing having at least one sidewall such that the casing includes an inner sidewall and an outer sidewall, the casing configured such that it has two opposing ends: a first end and a second end; a projectile configured to sit within and be retained by the casing and positioned adjacent to the first end; a propellant, the propellant configured between the projectile and the second end of the casing, the propellant configured to expand upon a firing event and project the projectile from the casing; and a coating comprising a fluoropolymer layer having a particulate boron nitride [dispersed] therein, wherein the coating is configured to cover at least one of the inner sidewall and the outer sidewall, such that at least one side of the substrate is covered by the coating.
An apparatus, comprising: an ammunition cartridge casing comprising a substrate configured to retain a projectile and a propellant, wherein the ammunition cartridge casing is configured with a coating thereon, wherein the coating includes: a fluoropolymer portion and an additive configured to be dispersed within the fluoropolymer portion.
In some embodiments, the fluoropolymer portion is configured to cover the substrate (e.g. completely encase the substrate).
In some embodiments, the additive comprises a ceramic additive.
In some embodiments, the ceramic additive is selected from the group consisting of: alumina, boron nitride, titania, and combinations thereof.
In some embodiments, the additive is present in a range of: at least 5 wt. % to not greater than 70 wt. %.
In some embodiments, the casing (ammunition cartridge with coating) is capable of withstanding pressure during a firing event yielding a pressure of at least 40 ksi.
In some embodiments, the casing (ammunition cartridge with coating) is capable of withstanding a firing event duration of at least 2.2 ms.
In some embodiments, the ammunition cartridge casing is capable of withstanding a temperature during a firing event of not greater than 3000 C.
In some embodiments, the coating is a sacrificial coating (i.e. is lost/burned off as a result of the firing event).
In some embodiments, the coating is configured on the outside of the case.
In some embodiments, the coating is configured on the inside of the case.
In some embodiments, the coating is configured to encase the substrate (e.g. completely cover and surround the inside, outside, and upper lip/opening, along with base of the case).
In some embodiments, the additive comprises a ceramic particulate material.
In some embodiments, the additive is selected from the group: alumina, titania, zirconia, boron nitride, cubic boron nitride, hexagonal boron nitride, boron nitride polymorphs, and combinations thereof. In some embodiments, the additive is surface treated. In some embodiments, the additive is surface treated with a polymer. In some embodiments, the additive is surface treated with a silicone based polymer and/or a polymethyl siloxane based polymer, where the polymer(s) is/are configured to cooperate with the coating and the substrate to promote a coated substrate having an surface-treated additive therein. Some non-limiting examples of silicone-based polymers (e.g. utilized with BN-additives include dimethicone (e.g. hydrophilic or hydrophobic dimethicone), methicone, and combinations thereof).
In some embodiments, the additive comprises uniformly sized granules.
In some embodiments, the additive comprises non-uniformly sized granules.
In some embodiments, the coating thickness ranges from 0.25 mil to 2.0 mil thick.
In some embodiments, the additive comprises a spherical shape.
In some embodiments, the additive comprises a plate-like shape.
In some embodiments, the additive comprises a polygonic cube.
In some embodiments, the additive comprises a prismatic shape (e.g. with an aspect ratio of approximately 1.0).
In some embodiments, the additive comprises a whisker shape (e.g. thin-rod shaped).
In some embodiments, the additive comprises a discoidal shape (e.g. circular flat shape).
In some embodiments, via visual observation, the casing does not exhibit a burn through event.
In some embodiments, via visual observation, the casing does not exhibit burning.
In some embodiments, via visual observation, the casing does not exhibit erosion.
In some embodiments, via visual observation, the casing does not exhibit melting.
In some embodiments, the coating is configured to insulate the substrate from the heat and pressure of the firing event.
In some embodiments, the coating is configured to isolate the substrate from contact with the gas released during the firing event (i.e. gas caused by ignition of propellant).
In some embodiments, the coating comprises an organic conformal coating.
In some embodiments, the coating comprises a fluoropolymer.
In some embodiments, the coating comprises a fluoropolymer; a solvent, and at least one additive.
An apparatus, comprising: a cartridge case comprising a substrate (e.g. Al, Ti, brass, steel, plastic), the cartridge case having: a base, a perimetrical sidewall configured to surround the base and extend upward from the base, and an open, upper end, and a coating on the base and the perimetrical sidewall of the cartridge case; wherein, via the coating, the cartridge case does not exhibit burn-through during a firing event that has a duration of greater than two milliseconds, where the firing event produces a gas having pressure of at least 40 ksi and a temperature not greater than 3000° C.
A method, comprising: forming a cartridge casing from a substrate material to provide a body having at least one sidewall, the cartridge casing having a first end and a second end, wherein the cartridge casing is configured to retain a projectile and a propellant; coating a cartridge casing with a layer of fluropolymer including a ceramic particulate dispersed therein; drying (curing) the coating to remove a solvent from the coating and set the coating onto the surface of the substrate (e.g. inner sidewall and/or outer sidewall); positioning the propellant and the projectile within the casing; forming an ammunition cartridge.
In some embodiments, coating comprises: spraying, dipping, brushing/painting, rolling, and combinations thereof.
In some embodiments, the method comprises cleaning the surface of the substrate prior to coating the substrate with a fluoropolymer.
In some embodiments, the method comprises deoxidizing the surface of the substrate (e.g. when the substrate is an aluminum alloy) prior to coating the substrate with a fluoropolymer.
In some embodiments, the coated case comprises: a chemical compatibility (i.e. between the coating and the propellants retained in the case (charge and primer)).
In some embodiments, the coated case comprises: a corrosion resistance (e.g. measured as a shelf life and/or resistance to moisture-rich environment).
In some embodiments, the coated case comprises: a coefficient of friction sufficient to reduce, prevent, and/or eliminate galling and/or spalling of the barrel and/or case. In some embodiments, when the coated case comprises an aluminum alloy substrate, the coefficient of friction is less than 0.45.
In some embodiments, the coated case comprises: a thermal resistance (i.e. sufficient to withstand storage at hot temperatures, fire resistance, and/or being loaded into a firearm with a preheated barrel (e.g. through repeated, previous firing events)).
In some embodiments, the coated case comprises: a propellant resistance (i.e. does not undergo corrosion and/or degradation when in contact with the powder/charge).
In some embodiments, the coated case comprises: a waterproof case capable of being immersed/submerged in a liquid (water) without losing its ability to fire (i.e. primer, charge, and case components remain intact). In some embodiments, the coated case comprises an abrasion resistance (as measured in the coating or in the ability of the coating to reduce, prevent, and/or eliminate abrasion of the underlying substrate (case).
In some embodiments, the coating is configured to protect a substrate material (e.g. metal, polymer) during a short duration, high temperature heating event (e.g. rifle shot).
In some embodiments, the casing components (coating and substrate material) are specifically configured as a system. In some embodiments, the substrate material is configured to provide mechanical strength (e.g. strength, stiffness, fracture toughness and other mechanical properties) while the coating (e.g. including ceramics or ceramic composite materials) is configured to provide thermal protection and chemical protection to the substrate (e.g. thermal insulating, corrosion resistant and abrasion resistant properties).
In some embodiments, the substrate comprises a thermal limit below the temperature of the firing event. However, the system/combination of substrate and coating material is sufficient to reduce, prevent, and/or eliminate heating the substrate to its thermal limit during the short duration of the firing event.
In some embodiments, the coating thickness is engineered to maintain the substrate temperature low enough during the firing event to prevent it from degrading.
This application is a non-provisional of and claims priority to U.S. Application Ser. No. 62/078,633 entitled “Coated Substrate Systems and Methods” filed on Nov. 12, 2014, which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62078633 | Nov 2014 | US |
