Tool Steels for Blades: M2 vs. D2?

Gryffin

Gryffin

Joined
Dec 27, 2004
Messages
1,500
Just read on other form, some guy asking about how the Benchmade 710HS in M2 stacks up against the regular 710 in 154CM, which got me thinking...

I know some of the limited edition Benchmade blades use D2 steel, and it's always coated like their M2 blades. I own one, a 921GRY, and it's a cutting ANIMAL. I also have a few Queens in D2, ditto.

That got me thinking about D2 vs. M2...

Both are tool steels, so I assume they're comparable in terms of hardness, toughness and edge retension. Is this accurate? If not, which one holds an edge better?

Also, I usually see D2 used without any special coating, but BM always coats their M2s. And I've heard some folks state that D2 is fairly resistant to corrosion for a non-stainless steel. How does uncoated M2 compare to D2 that way? How does it stack up to more common carbon steel like 1095, Case CV or Schrade's carbon steel?

So, where am I going with this?

One of most favoritest knives is my Benchmade McHenry & Williams 710. It's just about perfect, except I wish it had a D2 blade. I'm not about to cannibalize a $200 1-of-50 limited edition just to get a D2 blade for it, so I've been thinking of getting a 710HS and removing the BT finish (I prefer a polished blade; 4" of black blade tends to wig out the sheeple here in Joisey!). If M2 is as good as D2 in corrosion resistance and edge holding, I think I'd be one very happy boy. :D

Thanks for any input you can give me!
 
at least for me it does. D2 is an "almost" stainless steel. DO NOT remove the coating from an M2 blade, it is there for a reason. Go to Spyderco knives, and get an Edge U Cation. :D

That is an actual heading that they have in the top banner. Check it out, it has everything you need to know about knives, but did not think about asking.

Best Regards,

STeven Garsson
 
D2 has 11-13% Chromium
M2 has 3.75-4.5%

M2 also has a lot more Molybdenum than D2, has more Tungsten & more than twice as much Vanadium than D2.
so, how does it add up?

M2 is tougher, more wear resistant & holds a better edge than D2 but it rusts very easily!
hope this helps
 
The way i understand it (from purely theoretical sources) M2 is a high-temperature tool steel (high-speed steel) while D2 is borderline between cold working and high-temp.

Both exibit increase in hardness with increase in tempering temperature, unlike your regular cold-working steel where hardness drops monotonously with increase in temperature. Both can apparently attain relatively high hardness (63+HRC). M2 has considerably higher hardening temperature (~200 deg C higher than D2). So much for theory :)

I imagine in practice M2 (as HSS) is slightly more expensive, requires more expensive equipment and is less corrosion-resistant due to its composition. Both D2 and M2 allegedly make great cutting tools (knife blades, reamers, etc.) but i'd obviously expect M2 to perform better in higher temperatures; D2 begins to drop in hardness at 500+ deg C (932 deg F - not exactly the temperature range where you'd use your knife anyway - while M2 exhibits a secondary hardness peak there and holds on beyond 600 degrees C.

Graphics comparison that i've found online (top picture is D2, bottom is M2, sorry about the size of the images, i linked them directly from where i found them :) ):

ocr12vm.gif


brm2.gif
 
Crap. So it looks like I either need to find a D2 blade for mine, or get used to the black coating. Of course, that coating will wear...

Or, I could just keep my 710 in 154CM, and learn to be happy with what I have! :D

Thanks for the input, I knew I was asking in the right place!!
 
M2 perform better at high temperature ?? Well it was designed for tooling that gets hot in use like like production planer blades for the woodworking industry .Are you going to use your knife so fast and furious that it get very hot ?...As an ordinary knife steel it will be more wear resistant than D2 but will rust .D2 is called a semi stainless steel for knives but in my experience it's stainless .D2 is not quite as wear resistant ,easier to sharpen , doesn't rust, more practical as a knife blade.
 
Gryffin said:
That got me thinking about D2 vs. M2...

Both are tool steels, so I assume they're comparable in terms of hardness, toughness and edge retension. Is this accurate? If not, which one holds an edge better?
Click to expand...

D2's grain structure is much coarser than M2's. Therefore, the latter will take a finer edge. M2 is usually hardened to a higher RC and it's the superior steel as far as edge-holding is concerned.
However, D2 is "semi-stainless" while M2 will rust readily if not taken care of properly.
 
As said above, D2 is a "semi-stainless" steel. To be considered "stainless", chromium content needs to be 13% or higher. This isn't really a scientific principle, just an industry agreement standard. D2 generally has 10-13% chromium, depending on manufacturer. The D2 Benchmade uses, from Crucible, has 12% chromium. For comparison, 154CM/ATS-34 and S30V have 14% chromium, and VG-10 has 14.5-15.5% (these make up the majority of high-end knives).

To offset the softness the chromium adds, D2 has quite a bit more carbon than most other tool steels like M2 or A2. This allows it to be hardened a bit more than the stainless steels like 154CM or S30V. However, because of this, and the rest of its makeup, D2 has a much larger crystaline structure than most other steels (as QS mentioned above). I remember reading once that it's something like 15X the size of ATS-34. This means getting a polished edge with D2 is much more difficult than with most other steels. In practice, I don't think this really makes much of a difference. I have a few D2 blades, and they all pop hair with ease with a few strokes on a Sharpmaker. The real downside in practice is that D2 is very time consuming to sharpen. The upside being of course that it holds an edge for a very long time.

I personally would not want to carry a pocket knife made in M2 if it wasn't coated. Even then, I'd worry a bit about the edge. I don't have any in M2, but I have a couple (Severtechs) in A2. Keep it dry, and the edge shouldn't rust away, or even really tarnish. I expect M2 would be similar.

D2, being only "semi-stainless" will require a bit more attention than a typical stainless knife, but unlike an uncoated high-carbon blade, you don't have to worry about it rusting if you look at it wrong. Perhaps it's the dry Arizona air, but I've never seen even the remotest hint of oxidation on any of my D2 balisongs, and I don't really bother keeping them constantly oiled or inspect them every night (and yes, I do use a couple of them as EDCs, like the 41MC and 42-400). Benchmade doesn't always coat their D2. Some are coated, but so are some of their 154CM blades, and these don't really need a coating either, at least in my environment. The coating is more for people in very humid environs, people who are a little more lax about the upkeep of their knives, or for people who just like the way black blades look.

So in terms of actual use, M2 is a better all around cutter. Finer grain structure, better wear characteristics, easier to sharpen. But there's a reason BM coats it. A D2 blade will give almost as good wear characterstics and doesn't require a coating or as much upkeep, but will be more difficult to sharpen.
 
Planterz said:
I personally would not want to carry a pocket knife made in M2 if it wasn't coated. Even then, I'd worry a bit about the edge. I don't have any in M2, but I have a couple (Severtechs) in A2. Keep it dry, and the edge shouldn't rust away, or even really tarnish. I expect M2 would be similar.
Click to expand...

I agree wi9th Planterz's statements except for the above. Man, you live in Tucson and are saying that? I have carried A2 and M2 pocketknives, and just keep a light coat on them, and they are fine. With some of the newer anti-rust products out there, you don't even have to worry tto much about oilstains on your clothes. :D
 
Greeting's Guy's
im not here trying to argue with anyone ,but all the knives ive made from either D-2 or M-2 seem to be pretty good in the rust resistant area . Please remember im in the Rainy cold N.W where many metal's will get eaten up quickly by moisture . ive found that if the blade is finished to a high satin it will rust easily , if it is mirror or very close to it it will repel the moisture .
i store many of the knives ive made in the leather cases and still no rust ! What does it mean ? i don't know .i like both steel's beacuse they do take a lot of stuff that other knives wont /can't both will take a great edge that shaves big bald patches with ease . i use a M-2 blade for all Leather work i sharpen it twice a year no B.S and cut alot of 1/16 , 1/8,1/4 thick leather with this it glides like a straight razor each time . As i stated in the begining of my post Im not Here to argue with anyone !! im just trying to educate a little . Planterz/ Storm/ Mete ill send you each a small piece if needed just so you don't think im full of it .
 
I have removed a black coating from both my 710HS and 140HS. Completly from 140hs and slightly just to get rid of the scratches. I am planning to mirror polish them in the future. In my humble opinion BC really sucks, it scratches off, leaving your blade look terrible. And by the way if you even have it, like on a new knife, there still will be the edge and the buttom side of the blade uncoated. I always wipe off my knives after cutting food, no matter if it's stainless or tool steel, and never had any rust problems yet. And yes, I live in San Diego, next to the ocean, pretty humid in here. I would rather take a little bit more care than have to deal with ugly scratches. Here is a picture: http://pg.photos.yahoo.com/ph/ioumatov@sbcglobal.net/detail?.dir=cb4d&.dnm=132b.jpg&.src=ph
 
If you really want to take the coating off of an M2 blade, mirror finishing the blade will offer a little bit of protection.

Generally speaking, a coated blade has something like a rough satin finish under the coating (to make the coating stick better), and this rough surface will capture lots of gunk and moisture.
 
No personal experience here, but from what I have read, I got the impression that M2 was tougher, but D2 more wear resistant (partially due to the larger carbides)?
 
If it scratches off it's probaly not BC (boron carbide) I think benchmade is still using their teflon finish (BT) on the M2 blades.
 
I have had 3 people tell me that their D2 blades rusted. They were all three stored in leather sheaths and left there for several months until next hunting season. One of them was one that I made for one of my sons and it rusted pretty bad. He just washed and dried it, did not use anything to prevent rust.
 
Walt2 said:
I have had 3 people tell me that their D2 blades rusted. They were all three stored in leather sheaths and left there for several months until next hunting season.
Click to expand...
Well there's the problem right there. The chemicals used to tan, treat, and dye leather can cause serious corrosion to steel. Not to mention any moisture that might be in the leather or on the blade.

Store knives with leather sheaths seperate from the sheaths.
 
Considering what was told on BM forums and other places M2 is a fine steel for cutting.

Considering all the datas i have seen i wouldn´t agree that it is tough. There is one difference between D2 and M2 in regards of breaking resistance that M2 takes more force to break it. It will bend maybe at max. to 30° but will crack as immidiatly as D2 would do. Don´t try this!

D2 can be offered as fine grained as M2 if you choose a nearly same heat treatment. No manufacturer does so. That way both will deliver a combination of small and large carbides providing nices wear resistant edges.

I wouldn´t recommend both steels for razor blades or the like for their little toughness or ability to bend. On blade geometries, edc like (3 mm sabre grind or 4mm + full flat) they will perform very well. But D2, as offered regulary, tends to take a more rough edge instead of M2, so my choice would be M2.

So, after holding a BM 140HS i knew why people were so exited about it. But it is not tough, just strong in average thicknes as said before. Both will perform badly as choppers.

As far as rust goes. After seeing how late a pure carbon (0,75% carbon) rusts, i don´t care about it anymore. Cut fat after sour and keep the blade clean and the pivot lubed (that´s no difference to stain less to me) and everything should be fine.

BM offered an 805 in M2 in January and it sell in a second. So i think, D2 might be more common but if BM would make more LE in M2 they will sell sooner.
 
You must log in or register to reply here.
Back
Top