Has anyone here used or tested SM 100 Nitinol yet?

Salem Straub

Salem Straub

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Oct 20, 2008
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I got a request for a quote on a knife using this blade alloy. I have been researching it, but can't find results from anyone having put it to hard use. Specifically, it appears that blades made from it might be wimpy specifically in lateral bend resistance/stiffness. Also, can it be brazed well, as in a stick tang extension?

I talked to Chuck Bybee about it, who gave me an underwhelming impression of it. I know that the industry is susceptible to hype with new products, and there is certainly a lot surrounding this stuff. Also, it costs a LOT. So, I want to give my customer a balanced perspective from which to make a decision.

Thanks in advance to any and all.
 
I did metallurgy in for the company that originally invented it which sold the Nitinol business to a French company in a move based on short-sighted stupidity. It is a shape memory alloy, tell it what shape you want, then deform it, heating it will return it to the shape it was set to (could make the JS testing amusing, train it to a 90 degree bend, straighten it then lightly heat it for bending) The stuff is hard yes (I forgot what kind of Rockwells) it is extremely abrasion resistant, it will fight you at every step, the only thing that will really etch it is hydroflouric acid. I used to hate it when it showed up in my lab for testing (which was thankfully not often) I was originally going to say don't make a knife out of it, but the more I thought about it the more I realized that it might be interesting, not as hard as steel can get, but has some interesting properties. Start small!

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I was just about to embark on a project using this material myself, and I am very interested if anybody has any other info
 
I've got the same questions/concerns. I've never seen anybody actually use a knife made from it. It is so costly, it lends itself to the "bragging rights" crowd. It could be the best ever for all I know, just too early to tell.
 
All kinds of superlatives are being tossed around about it out there- but apparently mostly by the "bragging rights crowd" (so true, that's great) and by the manufacturer. There are a couple makers out there saying it's great too, but seemingly without any real objective data on field testing and practical limits.

The little I know from research:
Alloy is nominally 60% nickel, 40% titanium
Hardens in oil. From Summit alloy's site: “To harden it after profiling, we recommended 1800F with a 30 minute hold followed by an oil quench – this will get you to Rc 60. We then do a stabilization treatment of 600F with a 4 hour hold air cooled.”

Hardness attainable up to 62 Rc. Factory supplied in "soft state" of around 35 Rc. Needs carbide drills or bandsaw blades.

Classified by NASA as "corrosion proof."

Technically a reactive metal that can be anodized. Anodizing this material has proven very hard to do though, requiring voltages up to 500 volts at .4 amps for a simple bronze color. Cathode may need to be 3x the surface area of the workpiece.

Heat treating results in a very hard oxide coating on the surface, measured at 72 Rc.

It is lighter than steel, not as dense, and non-magnetic.

Apparently the earlier generation of NiTiNOL had problems with fine structure that would apply to knife blades- Summit states that by using particle metallurgy, this has been dealt with. Objective knife specific testing data would be good here.

Low Young's modulus. Manufacturer states similar to titanium when in hardened state. Does not state what alloy of titanium...

Supposedly superelastic. Specific data on stiffness apparently "not yet compiled."

I read some references to austenite, etc... but I do not know by what mechanism this hardens. It would seem not to be precipitation hardening, but can't be martensite either... it's totally non-ferrous, for Pete's sake. I'd like to find out. I saw links to a few technical papers about it, but I'm no Kevin Cashen or Roman Landes- I didn't read them (yet) because it probably wouldn't sink in.

I saw that Cliff Stamp had asked some hard questions on a forum, directly to a rep (the owner?) of Summit, and was not given a direct or satisfactory reply (IMO.) It was also debated whether some of the stupendous figures tossed around by the manufacturer really applied to use in cutlery- and whether in some ways such properties could be actually detrimental. A Google search would find that discussion.

Could be good, could be bad. Anyone else?
 
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They use it in both medical and military; for the former it is a good mat'l for wire that access tight spaces and chosen for its superb flexibility as well as resistant to bodily fluids, a must for class III products. I had tried to cut it but it's tough enough to even make a dent. Summits did a rust test lately and the results for sm100 is excellent.
I had talked to Ferrum forge and many who had used it has been a loyal fan to it. Of course that number is small considering the price tag.
 
Salem, there are martinsite transformations in alloys other than steel such as Maraging "steel" [not really steel ] I don't remember what I read about the alloy but most likely it's a martinsite ,precipitation hardening alloy like the Maraging .

http://en.wikipedia.org/wiki/Nickel_titanium
Here's some technical stuff !
 
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My first question when i read about Nitinol was the edge retention.
The only thing that actually applied to the Military would be the EOD.
 
Isnt Nitinol the stuff in "muscle wire" that is used by some home robotic hobbyists. You put enough of a current through it to heat it up and it flexes a wee bit of and when it is cool it relaxes.
 
Thank you, Mete! I got on a reading tangent just now from your link, into related subjects. I just found out about matweb.com, what a great site that is. Anyway, germane to the discussion at hand, here is what I'm taking away so far:

This alloy, also known as nickel-titanium, does indeed exist in martensite and austenite phases. I did not know those terms were used outside ferrous metallurgy.

From what I read at Summit's site, they do not seem to be quite sure whether the material is fully isotropic. That is, it may be significantly stiffer along the axis of grain direction than across the axis of grain direction. PM manufacturing may obviate this, but they said they didn't know whether it mattered if blades were cut from the plate in the direction of rolling or not and that they'd appreciate data from the field. I guess that's all right, but for a company that claims this stuff will revolutionize cutlery and is the "perfect" material for blades, this is disconcertingly vague.

NiTiNOL, as discussed in the Wikipedia article, has quite a low modulus of elasticity (Young's modulus). That is, the measurement of an elastic material's stiffness or resistance to deflection under load.

A comparative chart of approximate Young's modulus values shows that A36 mild steel has a value of about 210 GPa. Aluminum is at 69 GPa. Reinforced concrete is at 30 GPa.

NiTiNOL is listed in the article as having a Ym value of 75-83 GPa in an austenitic state (a little lower than pure titanium) and a value of only 28-40 GPa in a martensitic state. A separate article from the TiNi Alloy Company listed these values at approximately 75 and 28 GPa, respectively. As it's used for cutlery in the martensitic state, it would appear to thus be equal or slightly less stiff than reinforced concrete (of the same thickness, Mete?) in a blade. I mean, that's less than half as stiff as aluminum.

On the other hand, in the martensitic state it has about 50% higher ultimate tensile strength than 1090 carbon steel. That sounds good, but given that at the same time the Young's is low, and the rockwell hardness higher, it confuses me.

If anyone cares to enlighten me about where I'm wrong, or right, or what additional information I should be seeking, I'd appreciate it. Also, I can't find anything related to Rockwell hardness values in aus or mar states other than very limited values from the manufacturer.
 
Bhamster said:
Isnt Nitinol the stuff in "muscle wire" that is used by some home robotic hobbyists. You put enough of a current through it to heat it up and it flexes a wee bit of and when it is cool it relaxes.
Click to expand...

Also used in older cell phone antennas and fishing lures. Oh, and some guy made a heat powered engine from it as a proof of concept. I've got several pieces of the wire in the garage but I doubt I will find a good use for them.
 
Also used in stents and in heart valves. I guess the stuff has an unreal fatigue limit, the highest known of any metal. When you consider that the heart beats millions of times a year, that's impressive.
 
Salem Straub said:
Thank you, Mete! I got on a reading tangent just now from your link, into related subjects. I just found out about matweb.com, what a great site that is. Anyway, germane to the discussion at hand, here is what I'm taking away so far:

This alloy, also known as nickel-titanium, does indeed exist in martensite and austenite phases. I did not know those terms were used outside ferrous metallurgy.

From what I read at Summit's site, they do not seem to be quite sure whether the material is fully isotropic. That is, it may be significantly stiffer along the axis of grain direction than across the axis of grain direction. PM manufacturing may obviate this, but they said they didn't know whether it mattered if blades were cut from the plate in the direction of rolling or not and that they'd appreciate data from the field. I guess that's all right, but for a company that claims this stuff will revolutionize cutlery and is the "perfect" material for blades, this is disconcertingly vague.

NiTiNOL, as discussed in the Wikipedia article, has quite a low modulus of elasticity (Young's modulus). That is, the measurement of an elastic material's stiffness or resistance to deflection under load.

A comparative chart of approximate Young's modulus values shows that A36 mild steel has a value of about 210 GPa. Aluminum is at 69 GPa. Reinforced concrete is at 30 GPa.

NiTiNOL is listed in the article as having a Ym value of 75-83 GPa in an austenitic state (a little lower than pure titanium) and a value of only 28-40 GPa in a martensitic state. A separate article from the TiNi Alloy Company listed these values at approximately 75 and 28 GPa, respectively. As it's used for cutlery in the martensitic state, it would appear to thus be equal or slightly less stiff than reinforced concrete (of the same thickness, Mete?) in a blade. I mean, that's less than half as stiff as aluminum.

On the other hand, in the martensitic state it has about 50% higher ultimate tensile strength than 1090 carbon steel. That sounds good, but given that at the same time the Young's is low, and the rockwell hardness higher, it confuses me.

If anyone cares to enlighten me about where I'm wrong, or right, or what additional information I should be seeking, I'd appreciate it. Also, I can't find anything related to Rockwell hardness values in aus or mar states other than very limited values from the manufacturer.
Click to expand...

Youngs Modulus is stiffness (resistance to bending before nonelastic yield) hardness (rockwell) is resistance to penetration which is used to approximate resistance to deformation which in steels translates somewhat well to resistance to edge rolling, tensile is resistance to elongation deformation and failure (how strong is this rope). People don't talk about Young's in steel as it is pretty much the same from steel to steel. I think it will give you a soft but abrasion resistant edge. You will not be able to make a razor thin edge with it and have it stay sharp, it might work with a 25-35 degree included angle

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