Are sintered metal parts actually better?

[KarateHottie93]

I've always been under the impression that sintered metal parts are cheap and just not on the level of a good forged, or even cast part. Every metal firearm part I've ever had break that wasn't a spring was made from powdered metal so I may even have a biased against it.

I have very little knowledge of metallurgy in the grand scheme of things.

From everything I've heard though, powdered metal is apparently supposed to be much cheaper and easier to produce. Well I've recently been getting big into swords. They're pretty much all forged. That's great. Well then I started learning about knives. Again, that's great. Everyone loves knives. One thing that immediately stood out to me though is that all these ultra high end $800-$1000+ knives you see...they're are all being made with the latest and greatest powdered steel.

I even looked at some knife forums where some guy asked why swords were still made with folded steel over powdered steel. A lot of people were going on about how antiquated folded steel is and how superior powdered metal it. It was like a cult.

All I can think is that either the high end knife market is the biggest sham in years, or that everyone else has got powdered metal all wrong.

 

[Diamondback]

I've always been under the impression that sintered metal parts are cheap and just not on the level of a good forged, or even cast part. Every metal firearm part I've ever had break that wasn't a spring was made from powdered metal so I may even have a biased against it.

I have very little knowledge of metallurgy in the grand scheme of things.

From everything I've heard though, powdered metal is apparently supposed to be much cheaper and easier to produce. Well I've recently been getting big into swords. They're pretty much all forged. That's great. Well then I started learning about knives. Again, that's great. Everyone loves knives. One thing that immediately stood out to me though is that all these ultra high end $800-$1000+ knives you see...they're are all being made with the latest and greatest powdered steel.

I even looked at some knife forums where some guy asked why swords were still made with folded steel over powdered steel. A lot of people were going on about how antiquated folded steel is and how superior powdered metal it. It was like a cult.

All I can think is that either the high end knife market is the biggest sham in years, or that everyone else has got powdered metal all wrong.

I have only a basic 101 understanding of the MIM process...but it is my understanding that there are two critical steps...
the debinding and the sintering steps which are critical to making sure the part has the correct hardness. If either of those steps aren’t done correctly, you can get a part that’s too soft or a part that’s too hard and thus brittle...the initial formula has to be right. The big weakness in the MIM process is quality control.

State-of-the-art MIM technology, the latest in metal injection molded knife blade construction as done by Carpenter and Crucible uses advance metal forming techniques that produce very tight tolerances. Performed in a vacuum, it is common to reach 96-99% solid density. The end-product metal has comparable mechanical and physical properties with annealed parts made using classic metalworking methods. In other words, when done with precision, the MIM process can yield a part with exceptionally high strength and very good wear resistance. It's how you bake the cake that counts.

 

[JohnKSa]

The CPM process is different from the MIM process. The CPM particles are essentially welded into one piece via the application of extremely high pressure and temperatures approximately the same as those used for forging. This results in an ingot that is, for all intents and purposes, identical to one that was made via conventional means, but with much more tightly controlled homogeneity.

MIM involves mixing a binder with metal powder, heating it so the mass binds together and then injection molding the result. Then the binder is eliminated from the molded part by a heating/sintering process that I don't really understand. Although this last step results in a lot of shrinkage, the process is very predictable so the final piece's shape and dimension can be very precise.

Independent of all of that, if MIM is done right and the resulting parts are used where appropriate, it should never be a problem. We see gun parts made out of plastic, aluminum and even ZAMAK/die-cast metal in some cases. All of those materials can work when they are used appropriately, but any of them could be a huge problem if the designer/manufacturer was inept or cut corners.

I think, in general, people are best served by picking products made by a reputable and established manufacturer, known for making quality products and for standing behind them, and then leaving the manufacturing details and design decisions to them. Put another way, I'd take a gun full of MIM from a solid manufacturer every time over a gun that's made from 100% forged parts but comes from a company that has a reputation for poor QC.

 

[DMW1116]

I can’t speak much in the MIM process other than to say it is not the same process used for high end knife steel.

That is particle or powder metal technology and quite different. The alloy determines the process and many CPM steels can’t effectively be made using conventional methods.

With only one or two exceptions, I wouldn’t want a sword made from a powdered/particle steel. I’m fine with one from conventional steel of an appropriate alloy either forged or machined as long as the maker knows what they’re doing.

ETA: the biggest difference is MIM is a higher temperature process at or just above the melting point and is basically a casting process. Powder metals are solid processes typically except in some cases during the powder manufacturing. Forming parts or plate is done just below the melting point.

 

[DMW1116]

So a little more research reveals my first statement about not being able to speak on MIM processing was the most important part of the above post. When I first heard of MIM back in the 90s it was essentially done in the “slushy” phase just before complete melting. That is evidently not the way it’s done and I may be getting it mixed up with something else.

 

[JDeere]

MIM has come a long way since the 90s and early 2000s bad rap. Of course that bad rap follows it today thanks to the internet...ymmv

 

[jar]

Even ZAMAK when well done is great. Gillette started using ZAMAK for the cap on their double edged razors around the time of the Korean War. The cap is the critical component that holds that naked really really sharp blade in place as you use it against your neck. I have quite a few of them and still, even seventy years later, they still work as well as they did when new.

 

[StrawHat]

Ruger advertised they used sintered metal in their revolvers years ago, before MIM became the rage. (Or maybe sintered is the same as MIM).

I have several revolvers with sintered parts, no problems with them so far.

Kevin

 

[PapaG]

MIMM and compacted sintered metal are two different processes. Both produce good durable parts. At CAT we set up a whole facility in Rockwood, TN, to produce a wide variety of powdered metal parts. Advanced Compaction Technologies.

 

[mcb]

Modern MIM parts are nearly as good as a billet of the same alloy. If the MIM parts are designed for and use the HIP (Hot Isostatic Pressing) process the material properties are indistinguishable from a forging of the same alloy. With modern MIM parts the alloy used is as important as the process. A MIM part made from S7 tool steel powder will have significantly better material properties than a forge part from 1018 low carbon steel.

The gun industry was a very early adopter of and even helped mature the MIM technology. Thus a lot of those early learning lessons got shared with the gun community and the failures thus earned the process a bad name. Since those early days the technology has matured a lot and more importantly the next generation of engineers that "grew-up" using the technology are now in place. They know how to make the best use of the technology better than the previous generation.

MIM is basically the same as casting or forging in the sense that it is a quick and cheap way to get raw material into a net final shape or near net final shape reducing or eliminating the costly machining. MIM does this better than casting or forging because it can capture finer features and can more often result in parts that require no post machining.

ie S&W has made barrels for the 380 Body guard using the MIM process with no post machining. The barrels, including rifling, were all MIM'ed to final shape.

 

[JohnKSa]

With only one or two exceptions, I wouldn’t want a sword made from a powdered/particle steel. I’m fine with one from conventional steel of an appropriate alloy either forged or machined as long as the maker knows what they’re doing.

Generally speaking, powdered metallurgy is used to make more complicated alloys, which, while they have excellent properties for smaller knives (and other similar applications) are not ideal for very large knives or swords. Conventional techniques are more than adequate for the simpler alloys that are the best choice for large knives or swords.

 

[DMW1116]

Generally speaking, powdered metallurgy is used to make more complicated alloys, which, while they have excellent properties for smaller knives (and other similar applications) are not ideal for very large knives or swords. Conventional techniques are more than adequate for the simpler alloys that are the best choice for large knives or swords.

On a personal level, I have some odd requirements for that type of cutting tool. I'm not concerned with edge holding as far as abrasive resistance. The edge will get damaged long before that happens. I want ease of repair and shaping along with pretty bulletproof durability.

 

[JohnKSa]

Those aren't odd requirements at all.

The simple alloys are inherently "tougher"--they resist breakage from impact/flexing much better--and are therefore a much better choice for large knives that might be used for chopping or for swords. There's no need to make that kind of alloy using CPM and incur the extra expense; it can be made using conventional techniques.

 

[Jim Watson]

Right. As I understand it, CPM is for fancy alloying, MIM is for one pass production, molded to shape ready to use.
I don't know how near net shape the sintered parts in early Colt Mk III revolvers were.

Swords? All that traditional layer forging was to get a serviceable blade out of crap materials. Nowadays it is showboating. A martial arts friend pointed out that a major big cutting contest was won with a "mono steel" blade versus the laboriously forged repros.

 

[JohnKSa]

Yup. While it's certainly possible to improve the overall characteristics of a blade by doing layered steel properly, most of what's done these days is purely for decorative purposes.

 

[DMW1116]

The CPM process used for high end knife, tool, and die steels can make plate, sheet, and bar standard steel shapes. MIM is evidently limited to smaller parts. The MIM process may leave up to 4% porosity by volume, which can be desirable. It’s also possible to get rid of all porosity. The CPM products are typically hot rolled after sintering, removing any porosity.

 

[KarateHottie93]

Well it’s nice to know that MIM and CPM are completely different things.

I knew the revolver section would be able to give me the answers I needed.

 

[hemiram]

The connecting rods in most cars and trucks, and the gears in your power tools are almost all made from some sort of powdered metal process.

 

[Jonesy814]

S&W has been using MIM parts for at least 25 years. If those parts failed more often than the older forged parts it would be all over the internet

 

[Bearcat1982]

large knives and swords are made of CPM steel though. CPM 3V is a great choice for a large blade.

 

[Jim Watson]

If you want a "Damascus" slide on your next custom 1911, a Caspian is made from Swedish Damasteel, a powder metal product of two alloys.
Cabot will use one made by layer forging.

It occurs to me that we hear more reports of flawed MIM in 1911s than other guns. I think because the 1911 parts are directly copied in a material not used when designed. Other guns generally incorporate the mechanical properties of the new stuff. A Smith & Wesson revolver operates in the same general way as ever, but the parts are proportioned, contoured, and mounted to suit the material of construction.

 

[DMW1116]

large knives and swords are made of CPM steel though. CPM 3V is a great choice for a large blade.

With a few exceptions I would not want CPM steels for those types of blades. Exceptions would be single use blades in non-damaging applications. For instance I want a long tanto style blade for demo type cutting of empty water bottles. Basically any steel would do but I have some M2 at 65 HRc that is perfectly acceptable.

 

[Taroman]

If you are afraid of MIM, don't fly on a jet airliner (as if there was any other kind). Jet engines are full of MIM parts.
Only firearm part failures I have had in 40+ years of shooting were forged.
Extractor on a Colt 1911 broke while I was qualification firing at Fort Stewart.
Despite that I still shot Expert.
Bolt on my S&W Model 60 while practicing:

 

[Bearcat1982]

not to argue but I think you should brush up on your steels. CPM 3V is a wildly tough Steel that holds a great edge. Alot of high end large knives are being made out of 3V including BUSSE's take on a tanto style short sword/knife
https://www.bussecombat.com/swamp-rat-free-rein-sr-3v-swamp-comp-finish/

https://www.dawsonknives.com/products/windstorm-scimitar-sword
If your into choppers and large knives you're missing out if your over looking steels like 3V. I think you just have a misunderstanding of the cpm process. There's CPM versions of older steels like D2, CPM D2. It creates less imperfections and CPM D2 out performs its predecessor. Creating a tougher blade. It's D2 with out the inherent problems with D2. I've enjoyed a bark river in cpm d2 quite a bit.

With a few exceptions I would not want CPM steels for those types of blades. Exceptions would be single use blades in non-damaging applications. For instance I want a long tanto style blade for demo type cutting of empty water bottles. Basically any steel would do but I have some M2 at 65 HRc that is perfectly acceptable.

I'll start a thread of cpm steel in large blades. In the non firing weapon sub forum here instead of bogging down this thread

 

[Dustbowl]

I admittedly don’t know much about the process but if you read a kuhnhausing gunsmithing book about 1911’s or Smith and Wessons he had about 3 pages devoted to bashing S&W for switching to MIM and the higher rate of wear and breakage he observed in those parts. I also have a bad history with it seeing as the amount of kimber extractors and small parts I’ve replaced. But maybe those books are a bit out of date.