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armeiro
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Posted: 11/26/2011 1:14:21 PM
[Last Edit: 11/26/2011 1:14:40 PM by armeiro]
Can Inconel be used for rifle barrels?

"Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys.[1] Inconel alloys are typically used in high temperature applications. It is often referred to in English as "Inco" (or occasionally "Iconel"). Common trade names for Inconel include: Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625 and Nicrofer 6020."

"Properties
Inconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies (see Arrhenius equation). Inconel's high temperature strength is developed by solid solution strengthening or precipitation strengthening, depending on the alloy. In age hardening or precipitation strengthening varieties, small amounts of niobium combine with nickel to form the intermetallic compound Ni3Nb or gamma prime (γ'). Gamma prime forms small cubic crystals that inhibit slip and creep effectively at elevated temperatures."

North American Aviation constructed the skin of the X-15 rocket plane out of an Inconel alloy known as "Inconel X"

http://en.wikipedia.org/wiki/Inconel

Research Project X-15 - The Air Force Rocket Plane
http://www.youtube.com/watch?v=hovf9bKrFfI
gerfungerpoken
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Posted: 11/26/2011 1:40:55 PM
Isn't it supposedly a major bitch to machine?
joe___223
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Posted: 11/26/2011 1:45:41 PM
Originally Posted By gerfungerpoken:
Isn't it supposedly a major bitch to machine?


yes

I wouldn't want to have to drill a deep hole in it. Sounds like a very expensive barrel

armeiro
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Posted: 11/26/2011 1:54:54 PM
Inconel alloys are oxidation and corrosion and high temperature resistant,does it have the same or more gas PSI resistance?
mr_hankie
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Posted: 11/26/2011 2:04:59 PM
[Last Edit: 11/26/2011 2:12:29 PM by mr_hankie]

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Posted: 11/26/2011 2:05:35 PM
[Last Edit: 11/26/2011 2:12:58 PM by mr_hankie]
Originally Posted By mr_hankie:
Originally Posted By gerfungerpoken:
Isn't it supposedly a major bitch to machine?


Dammed laptop has a hiccup
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Dodge223
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Posted: 11/26/2011 2:10:27 PM
Originally Posted By gerfungerpoken:
Isn't it supposedly a major bitch to machine?


Yes, and far more expensive than the regular barrel steels.
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Posted: 11/26/2011 2:11:26 PM
[Last Edit: 11/26/2011 2:11:59 PM by mr_hankie]
"In einer Mensch-zu-Mann-Kampf, ist der Gewinner, wer eine Runde in seinem Magazin hat"
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Posted: 11/26/2011 2:27:06 PM
We have flange gaskets made with it in our gas turbines. I like keithj's idea of using it for supprssor blast baffles or the baffles themselves. Or a goddamned pipe to beat the shit out of this tablet.

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Cdenmark
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Posted: 11/26/2011 2:39:00 PM
[Last Edit: 11/26/2011 2:41:01 PM by Cdenmark]
Used to use inconel valves exclusively in supercharged marine race engines and DEA chase boat engines. Well worth the extra coins over titanium or stainless. As for rifle barrels, costs would well exceed the purpose. Theory is correct though just not cost effective as stated above. Great for suppressors as also stated above.
57Octane
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Posted: 11/26/2011 2:44:59 PM
Isn't that what Armalite used to make the early AR-10 flash hiders? I think they switched from titanium to inconel.
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Posted: 11/26/2011 2:53:11 PM
The kac triple tap is EDM wire machined out of Inconel.
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Hal143
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Posted: 11/26/2011 3:27:04 PM
Not much I can add but when I worked for Martin Marietta as a saw operator we had bar stock of inconel as large as 8" x10" by 12+ feet. I remember cutting slabs from a 4" round rod on the Marvel saw would take 4-6 hours per cut and trash several blades. A beautiful metal. Just too expensive to machine in mass quanity.
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Posted: 11/26/2011 3:32:28 PM
Alot of the shafts in our downhole oil well pumps are inconel. We use it for the high HP applications
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Hognose
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Posted: 11/26/2011 4:40:43 PM
Can Inconel be used for rifle barrels?


I've never heard of anyone doing it. Not even for aerospace weapons applications where you need extreme rates of fire.

In the application that North American used Inconel X for (hypersonic skin), other engineers used titanium alloys, and the Russians used stainless steel in the MG-25 and -31. But the MiGs had very different mission profiles than the X-15 or the titanium-skinned A-12/SR-71 ships. The SR-71 could fly at over Mach 3 for hours (as far as I know the exact capabilities are still classified, even though the planes themselves grace museums worldwide). The X-15 had relatively short flights at up to M5. The MiGs are essentially point defense interceptors and they can just barely hit M3 for a few minutes (and are placarded against sustained high-Mach flight). So in theory one might substitute an Inconel alloy for stainless steel but I'm not sure what you would be buying, unless you had a way to sustain fire of rounds traveling in excess of M3.

Worth noting, that Scaled Composites has used carbon-reinforced epoxy in applications up to the Mach 3-4 range (SpaceShip One and SSTwo for example). Maybe they were onto something with the fiberglass barrel....?

The only chemical-powered guns I know of that have a hypersonic capability are tank main guns. As far as I know, they are made of steel, even though tens of millions of dollars/Euros/shekels/what-have-you are spent on modern tanks. (Just doing it in my head, the 120mm gun in the M1A1 has a m/v of about 1 mile per second, that's 3600 mph (1x60x60), divide 760 (sea level M1) and you have about Mach 4.7. The Russian 125mm is a little faster, IIRC). The 120mm gun is steel with a chrome bore, but the bore is only good for 50-250 rounds. The US (really German) and Russian guns are smoothbores, a rifled gun wears out even faster.

Western medium machine guns often have Stellite barrel liners to support sustained fire. http://www.stellite.com/ Stellite can be forged, although not to net shape like aluminum. (I don't know if Inconel can be forged, but I think not). Forging Stellite is hard on tooling. Machining it requires at minimum carbide tools.

I did work for a machine tool company that did have grinding applications for Inconel. (The parts were turbine spools for General Electric and P&W). The parts were machined, not forged. A jet turbine spindle is a pretty big hunk of metal, but these came to us already valued in the six figures. (We set up machines using scrap parts, of which the jet engine makers had all too many). Precision grinding Inconel was challenging even with diamond wheels. By the time we had the machines working, we lost money on each one.

There are a great deal of SAE papers on working with exotic materials, including Stellite, Inconel and Titanium. Of those, the easiest to work is Ti alloy. (cut slowly, lots of coolant, have extra blades/bits/wheels). If you've ever done anything with it, you'll think that is hard enough. It's worth taking a few classes at a nearby university, if it has a good engineering library.
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Posted: 11/26/2011 4:58:52 PM
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Posted: 11/26/2011 5:01:48 PM
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Posted: 11/26/2011 6:05:36 PM
[Last Edit: 11/26/2011 6:05:36 PM by coctailer]
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desmodue
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Posted: 11/26/2011 11:18:01 PM
[Last Edit: 11/26/2011 11:35:55 PM by desmodue]
Originally Posted By armeiro:
Can Inconel be used for rifle barrels?

"Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys.[1] Inconel alloys are typically used in high temperature applications. It is often referred to in English as "Inco" (or occasionally "Iconel"). Common trade names for Inconel include: Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625 and Nicrofer 6020."

"Properties
Inconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies (see Arrhenius equation). Inconel's high temperature strength is developed by solid solution strengthening or precipitation strengthening, depending on the alloy. In age hardening or precipitation strengthening varieties, small amounts of niobium combine with nickel to form the intermetallic compound Ni3Nb or gamma prime (γ'). Gamma prime forms small cubic crystals that inhibit slip and creep effectively at elevated temperatures."

North American Aviation constructed the skin of the X-15 rocket plane out of an Inconel alloy known as "Inconel X"

http://en.wikipedia.org/wiki/Inconel

Research Project X-15 - The Air Force Rocket Plane
http://www.youtube.com/watch?v=hovf9bKrFfI



Nickel based superalloys are a poor choice for rifle barrels. Inconel 625, Hastelloy X, SuperTherm, etc perform very well in high heat application or corrosive atmospheres, but since nickel is relatively soft, they are poor performers in high wear applications. Passivation on the surface layer will withstand extreme heat and resist corrosion in some very nasty solutions (look up a test solution known as "green death") But the passivation layer is largely nickel oxide it is quite easily damaged by high friction surface loads, like a bullet travelling at 3000 fps.

People tend to confuse nickel based superalloys with stainless steel. Stainless steel has a lot of iron in it, as where superalloys have little to no iron and very low carbon content, (Inco 625: 5% Iron and .10% carbon) This makes for poor anti-wear qualities. We can talk about face cubic centered and body cubic centered structures, intermetalic phases and creep resistance until we bore everyone to death. But none of that is related to wear, it is all related to heat and corrosion resistance.

On the other side of the superalloy game you have the wear resistant alloys. Stellite being one of the most widely recognized tradenames. These alloys are very hard and as such have excellent wear resistance properties. These alloys also have little to no iron but very high carbon content (1-2% not fractions of a percent) since nickel is soft it isn't used. But cobalt, chrome and tungsten are very hard, and make up the bulk of the alloy. Seems like the perfect solution. The alloy is hard, so it offers fantastic wear resistance properties, but it's next to impossible to machine, it can have cracking problems (hydrogen embrittlement as well as inter-granular attack) So, not really a good choice for rifle barrels.

Forging. Yes Inconel 625 can be forged, in fact forging is quite common and maximizes the properties of superalloys by further grain refinement. Unfortunately forging of nickel based alloys doesn't yield the same resulting strength increase as it does in carbon steel. Alloys are a lot like AR15s, someone always wants to know "what's the best one to buy?" The answer in both cases is the same...it depends on what you want to do with it. I've worked with nickel and cobalt based alloys my entire working life, they are pretty amazing. But even after 30 years of this, I'm still impressed at how good steel is for a lot of applications. There have been a lot of very smart people that have selected the material used for rifle barrels. Steel is pretty hard to beat.
JoshAston
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Posted: 11/27/2011 12:17:10 AM
Originally Posted By desmodue:
Stellite being one of the most widely recognized tradenames. These alloys are very hard and as such have excellent wear resistance properties. These alloys also have little to no iron but very high carbon content (1-2% not fractions of a percent) since nickel is soft it isn't used. But cobalt, chrome and tungsten are very hard, and make up the bulk of the alloy. Seems like the perfect solution. The alloy is hard, so it offers fantastic wear resistance properties, but it's next to impossible to machine, it can have cracking problems (hydrogen embrittlement as well as inter-granular attack) So, not really a good choice for rifle barrels.


Stellite is already used as liners in some machine gun barrels, to include the M2.
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HeavyMetal
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Posted: 11/27/2011 12:21:24 AM
Originally Posted By JoshAston:
Originally Posted By desmodue:
Stellite being one of the most widely recognized tradenames. These alloys are very hard and as such have excellent wear resistance properties. These alloys also have little to no iron but very high carbon content (1-2% not fractions of a percent) since nickel is soft it isn't used. But cobalt, chrome and tungsten are very hard, and make up the bulk of the alloy. Seems like the perfect solution. The alloy is hard, so it offers fantastic wear resistance properties, but it's next to impossible to machine, it can have cracking problems (hydrogen embrittlement as well as inter-granular attack) So, not really a good choice for rifle barrels.


Stellite is already used as liners in some machine gun barrels, to include the M2.


...and the M-60 series.
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Posted: 11/27/2011 1:57:43 AM
Wow, this thread is way over my head, but very interesting nonetheless!
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desmodue
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Posted: 11/27/2011 2:23:12 AM
That isn't really the same as making a barrel out of Stellite is it?

I have never had the opportunity to examine an M2 or an M60 barrel assembly. I was able to find drawings of the Browning 1919 machine gun barrel (dwg#D7162295) the drawing and the accompaning text indicates that it is a 3 piece design consisting of the main barrel tube, a 5" long Stellite insert in front of the chamber and a Screwed in chamber insert of an unnamed material. Interestingly the drawing has a note specifying that the 5" long Stellite insert's rifling and the tubes's rifling must mate within .010" of each other. I assume that means .010" maximum gap, not concentricity. All very interesting. I bet it was a real pain to finish cutting the rifling in that 5" section of Stellite. I would have liked to seen how this process unfolded, did they start trying to use a full 45" long Stellite liner and just keep shortening it until they found a length that they could cut rifling in?

text: http://browningmgs.com/Info/Barrels.htm

drawing: http://browningmgs.com/Info/Images/Barrels/fig23.jpg

Edit: More recent info from 2007 Sabre Defense. Honing Stellite inserts for 50 cal. barrels (they say the chamber and the first few inches are a Stellite insert) 10 shots in an 8" group at 100 feet?
http://www.designfax.net/news/archive/10-21-2008/stories/feature-2.asp
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Posted: 11/27/2011 5:03:13 AM
Does Microgroove rifling makes a diference comparing to normal rifling.
"MicroGroove Rifling
In 1953 Marlin Firearms was issued U.S. Patent 3,100,358 for what was named MicroGroove Rifling, which was a departure from the standard "Ballard," or cut rifling. One purpose of Microgroove rifling was to increase the speed of producing rifle barrels. Microgroove rifling is described in the patent as having 5 grooves for every 1/10 of an inch bore diameter, and that the driving side of each land would be "tangentially disposed" to prevent accumulating fouling in use.

Marlin introduced Microgroove rifling in their .22 rimfire barrels in July 1953, with 16 grooves that were .014" wide, and nominally .0015" deep. Ballard rifled barrels have grooves generally in the range of .069-.090" wide, and .0015-.003" deep. This change was marketed in the 1954 Marlin catalog, as having numerous advantages that this new form of rifling had, including better accuracy, ease of cleaning, elimination of gas leakage, higher velocities and lower chamber pressures. The catalog also claimed that Microgroove rifling did not distort the bullet jacket as deeply as Ballard rifling hence improving accuracy with jacketed bullets at standard velocity.

Designed for factory loaded ammunition, Microgroove barrels have a reputation for accuracy problems with centerfire ammunition handloaded with cast lead bullets due to the increased bore diameter generated by the shallow grooves. Use of oversized cast bullets has great effect on solving this problem, restoring accuracy with cast bullet handloads to levels seen from Ballard rifled barrels. Early Marlin .30-30 microgroove barrels had a twist rate of 1 turn in 10 inches optimized for factory ammunition with jacketed bullets; later Marlin .30-30 microgroove barrels show a twist rate of 1 turn in 10.5 inches which improves accuracy with cartridges loaded to lower velocity than standard."
http://en.wikipedia.org/wiki/Marlin_Firearms

Marlin Firearms MicroGroove Rifling article,from page 26.
http://www.gunsmagazine.com/1961issues/G0961.pdf

Are there AR-15s using this type of rifling,can it make easy to rifle a hard alloy barrel?
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Posted: 11/27/2011 7:21:18 AM
[Last Edit: 11/27/2011 7:24:04 AM by armeiro]
Picatinny cobalt alloys show promise for sustained firepower


Far right, engineer Vinny Leto holds one of the various cobalt alloy barrels produced using the flow forming technique. The shortest barrel was the first produced, followed by full length barrels without rifling and later a prototype with rifling like the one that was tested. Other team members, from left, Michael Hespos and Keith Koehler.

"PICATINNY ARSENAL, N.J. –– During a firefight, the last thing a machine gunner wants to do is stop fighting to change barrels, but that's how it has always been done with standard, single steel-barrel machine guns.

The reason for the barrel change is that at high temperatures barrels lose "strength properties," according to engineers working on a promising alternative.

One of the engineers is Vinny Leto, systems project engineer, of the Armament Research, Development and Engineering Center, or ARDEC, Weapons System Technology Directorate. During a test firing of a proof-of-concept barrel in December, Leto witnessed a measure of success with the High Performance Alloys for Weapons Applications Project.

During testing, the first rifled, cobalt-alloy machine gun barrel ever produced using the "flow forming" process consistently reached high temperatures without degraded performance.

The proof-of-concept barrel was made of an alloy that contains more than 50 percent of the metal cobalt. Cobalt alloys are erosion- and corrosion-resistant metals that are designed to retain high strength during long-term exposure to high temperatures.

Cobalt alloys are frequently used in the aerospace industry, such as the hot-gas section of turbine engines, explained Leto. Cobalt alloys are also used as short liners for machine gun barrels.

"If you look at steel in a machine gun environment, it gets very hot at a high rate of fire," said Leto. "The benefit of the cobalt alloy is that it is designed to operate in high-temperature, high-stress environments. It has the added benefits of corrosion and erosion resistance."

While cobalt alloy barrel liners have been produced for years, it is very difficult with existing machining techniques to impart rifling. "The material, for all of its phenomenal properties, is very difficult to manufacture and machine," said Leto.

Different from machining, flow-forming is an advanced process used to manufacture precise cylindrical components. The process consists of high-pressure rollers exerting pressure on the exterior of a cylinder, pressing material against a rod-called a mandrel-on the interior of the cylinder. For this project, the flow-forming process was modified to produce the rifling in the barrel bore.

More testing and data gathering will be required before engineers know if flow forming manufacturing can be achieved with the alloy.

Success, however, would provide warfighters with three potential benefits: lightening their load, increasing barrel service life, and giving them a barrel that could operate at higher temperatures compared to a steel barrel, Leto said.

Soldiers and Marines typically carry spare barrels into battle so that they have a cool barrel to exchange if they engage the enemy in a firefight, explained Leto. Having that strength at higher temperatures means that barrels may not need to be changed during a firefight, eliminating the need for the extra barrel and maintaining a steady stream of firepower.

Engineering team members met all of their proof-of-concept test objectives when they fired more than 24,000 rounds and achieved an 1,100 degrees barrel temperature. Leto said the alloy barrel was fired from the ARDEC-designed Advanced Remote/Robotic Armament System.

Steel begins to lose strength at approximately 1,000 degrees, Leto noted, and the test yielded data needed to assess and design the next round of improvements. The team is planning to produce another prototype that will be fired from a fielded infantry weapon later this year.

Previously, the engineers had produced a half-length barrel as an initial demonstration of the flow-forming process before moving on to manufacturing full-length barrels.

The Office of Naval Research assigned the engineers as principal investigators into the flow forming manufacturing technology. They are leveraging ARDEC's expertise with metallurgy and small arms design and analysis. Prototype testing will be conducted here at the Armament Technology Facility, which is ARDEC's small arms design and evaluation facility.

Previously, the engineers had worked with the Office of Naval Research in development of lightweight 60mm and 81mm mortar tubes made with a nickel-based alloy.

The team is also working with the Joint Services Small Arms Program, which is also based at Picatinny Arsenal. The JSSAP office oversees the day-to-day implementation of the plan by the joint services regarding the development and investment in small-arms technologies. "

http://www.army.mil/article/52605/picatinny-cobalt-alloys-promise-for-sustained-firepower
armeiro
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Posted: 11/27/2011 8:11:24 AM

MANUFACTURE PARTS MADE OF INCONEL
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