Understanding CTS-XHP

Robert Erickson

Robert Erickson

Knifemaker / Craftsman / Service Provider
Joined
Feb 2, 2014
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I'm intrigued by CTS-XHP steel. In doing a quick search on it I've seen it compared to CPMS30V and other so-called "super steels" in edge retention. In looking at it's chemistry it's remarkably similar to D-2, which makes sense in that D2 reportedly holds an edge well. It is, however, dissimilar chemically to S30V and the like. So where do CTS-XHP and D2 get their edge retension from? IIRC S30V etc get their edge retention from the added Vanadium. D2 and CTS-XHP are mostly carbon and Chromium with trace amounts of silicon, manganese, vanadium and molybdenum. Is it forming Chromium carbides?
 
The edge retention comes from chromium carbides. The extra vanadium in the "super steels" adds more fine vanadium carbides. Of the three steels mentioned, S30V will have a finer and harder edge. The large carbides on the CTS-XHP steel will make it very tough, but chromium carbides are larger, thus the edge sharpness is somewhat less ( mostly theoretical).

This should help compare them:
http://zknives.com/knives/steels/steelgraph.php?nm=CTS-XHP, D-2, S30V&hrn=1&gm=0
 
Thanks Stacy. What I'm ultimately getting at is finding cutlery steel that is low maintenance. The people I've made knives for, thus far, are not knife junkies that know how to or care about sharpening blades. They're also likely to leave them in the sink overnight. I love the sharpness that I can get with 52100 but I think I'm going to jump into some S30V or VN.
 
you could try talking to Ian Hall (Hall Handmade), I believe he is a user of this steel.
 
One of the reasons I went to CPM-S35VN for my stainless cutlery is that it has a good durable edge. It can be sharpened to a quite sharp edge, too.
 
These discussions about CPM154, 154cm, S30V, CTS-XHP and CPMS35VN are always interesting to me and I have wondered where does S90V fall in this lineup of steels in your opinions. I have always liked the edge that S90V will obtain.
 
Butch Harner works with XHP quite a bit too, or at least he did for a while.

I've only made one blade with XHP, but I'm very impressed with it. The edge retention is very, very good @ 58Rc (which is quite low for a "high edge-retention" blade), and the high toughness really surprised me.... really quite remarkable for a steel with so many chrome carbides. I did not have any particular trouble getting a good crisp fine edge on it. I think the main thing that makes it work so well is the high quality of the particle metallurgy involved.

It's really not appropriate to describe it as "stainless D2" for knife applications, because it's much tougher and much finer-grained than D2... although the chemistry is quite different, in practice I find it very comparable to Elmax... more like a "stainless CPM-3V". I think the reason they describe it as D2 on 'roids is that it was originally designed for plastic injection molding dies, and apparently the materials involved can be quite corrosive.

Anyway, it's outstanding steel by all accounts. Whether or not you really notice a difference in edge acuity/fineness, toughness/resistance to chipping, edge-holding etc. between it and S35VN or CPM-154 and so on will depend to some extent on the blade design, how thin you grind it, and how fine you sharpen it. They all have very good corrosion-resistance; if you require very high toughness and thin edges, XHP and Elmax are the better choices.

For pure sharpness, say if you want to go up to 20,000+ grit waterstones on a 15-degree inclusive edge, I suspect you'd be better off with a low-carbide stain-resistant steel like AEB-L. But of course you won't get as much abrasion-resistance without the carbides.

All steels mentioned here definitely work very well; none is a slouch. For lack of a better analogy, we're into the territory of comparing 'Vettes to Vipers... not jalopies to racecars. ;)
 
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Here's the chemistry as best as I can find between CPM D2 and XHP:
CTS-XHP chemistry: Carbon 1.60% Silicon 0.40% Manganese 0.50% 0.45% Chromium 16.00% Molybdenum 0.8% Sulfur 0.030%Max)
CPM-D2 chemistry C- 1.55 Mn- .37 S- .018 Si- .87 Ni- .11 Cr- 11.27 V- .91 W- .o61 Mo- .77 Co- .038 Cu-.080
The only appreciable difference that I can see is the amount of Chromium. I'm assuming that what makes D2 not take such a fine edge is the large Chromium carbides...how can adding more Chromium and therefore presumably more of the same carbides make for a finer grained steel? This whole metallurgy thing is fascinating! I'm just going to have to make more knives:D
 
rcetroy said:
hat I can see is the amount of Chromium. I'm assuming that what makes D2 not take such a fine edge is the large Chromium carbides...how can adding more Chromium and therefore presumably more of the same carbides make for a finer grained steel?
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Because of very clean, precise, third-generation particle metallurgy processes, that help separate every elemental component of the alloy into much smaller bits even before mixing them together, instead of big globs of elements and impurities that just get swirled together in a cauldron.

It may help to picture D2 as rather coarse concrete (a mix of martensitic/austenitic steel) with a few big chunks of raggedy rocks ( coarse carbides) in it here and there, compared to CTS-XHP as very fine clay (tempered martensitic steel) with many tiny, evenly-distributed pebbles (fine carbides) in it.

For a much smarter and more in-depth description of how this sort of thing really works in cutlery steels, please Google "micrographs of powder steels" , and a couple knifemakers named Kevin Cashen and Nathan the Machinist. Those cats are much better at explaining this stuff than I am.

Meanwhile... don't take my word for it. Get you some D2 and some 3V and some XHP and some Elmax... grind them all exactly the same way, and send the blades to a professional HT firm, to be run at the same Rockwell hardness. Then use them a lot and cut various stuff and beat the snot out of them and just see what happens. The practical differences will become apparent very, very kwickly. I've done that, and I will never buy D2 barstock for knifemaking again. YMMV.
 
Thanks James! Trying to wrap my brain around the metallurgy is an adventure. I've tried reading the paper by Verhoeven but my brain started to hurt too much. I'm kind of in that dabbling stage of knife making, trying to figure out what my favorite types of steel are. So I'll add those to the mix and have at it.
 
james terrio said:
Butch Harner works with XHP quite a bit too, or at least he did for a while.

I've only made one blade with XHP, but I'm very impressed with it. The edge retention is very, very good @ 58Rc (which is quite low for a "high edge-retention" blade), and the high toughness really surprised me.... really quite remarkable for a steel with so many chrome carbides. I did not have any particular trouble getting a good crisp fine edge on it. I think the main thing that makes it work so well is the high quality of the particle metallurgy involved.

It's really not appropriate to describe it as "stainless D2" for knife applications, because it's much tougher and much finer-grained than D2... although the chemistry is quite different, in practice I find it very comparable to Elmax... more like a "stainless CPM-3V". I think the reason they describe it as D2 on 'roids is that it was originally designed for plastic injection molding dies, and apparently the materials involved can be quite corrosive.

Anyway, it's outstanding steel by all accounts. Whether or not you really notice a difference in edge acuity/fineness, toughness/resistance to chipping, edge-holding etc. between it and S35VN or CPM-154 and so on will depend to some extent on the blade design, how thin you grind it, and how fine you sharpen it. They all have very good corrosion-resistance; if you require very high toughness and thin edges, XHP and Elmax are the better choices.

..........
Click to expand...

james terrio said:
Because of very clean, precise, third-generation particle metallurgy processes, that help separate every elemental component of the alloy into much smaller bits even before mixing them together, instead of big globs of elements and impurities that just get swirled together in a cauldron.

It may help to picture D2 as rather coarse concrete (a mix of martensitic/austenitic steel) with a few big chunks of raggedy rocks ( coarse carbides) in it here and there, compared to CTS-XHP as very fine clay (tempered martensitic steel) with many tiny, evenly-distributed pebbles (fine carbides) in it.

For a much smarter and more in-depth description of how this sort of thing really works in cutlery steels, please Google "micrographs of powder steels" , and a couple knifemakers named Kevin Cashen and Nathan the Machinist. Those cats are much better at explaining this stuff than I am.

Meanwhile... don't take my word for it. Get you some D2 and some 3V and some XHP and some Elmax... grind them all exactly the same way, and send the blades to a professional HT firm, to be run at the same Rockwell hardness. Then use them a lot and cut various stuff and beat the snot out of them and just see what happens. The practical differences will become apparent very, very kwickly. I've done that, and I will never buy D2 barstock for knifemaking again. YMMV.
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So JT (and everyone else who would chime in), which do you prefer if choosing from with CTS-XHP or ELMAX for "very high toughness and thin edges" (as in bushcrafty type knives)?
 
fmajor007 said:
So JT (and everyone else who would chime in), which do you prefer if choosing from with CTS-XHP or ELMAX for "very high toughness and thin edges" (as in bushcrafty type knives)?
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Whichever one is available in the size you want, and/or whichever one you can get at a better price. I honestly feel they're very comparable in all aspects of practical performance, and I'd have no trouble recommending either one of them for bushcrafty knives with thin edges. :)
 
james terrio said:
Whichever one is available in the size you want, and/or whichever one you can get at a better price. I honestly feel they're very comparable in all aspects of practical performance, and I'd have no trouble recommending either one of them for bushcrafty knives with thin edges. :)
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Interesting.... I didn't know you were a politician?!? ;)

Kidding aside, thanks for your opinion.

I have it from a *very* good source (ie it cannot be a better source....) that EnZo is considering offering their Trapper in ELMAX. It wouldn't be for about 8 months, but seems to be a distinct possibility.

Since I learned about this possibiliy, I've been reading and re-reading as much as I can about all these nifty super-steels. As always, there seems to be a trade-off with materials and ELMAX (and as I've just learned CTS-XHP) does a superb job at striking a balance (along with M390, et al).
 
fmajor007 said:
Interesting.... I didn't know you were a politician?!? ;) Kidding aside, thanks for your opinion.
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Not a "political answer" at all, that's my honest opinion. There's more than one way to skin a cat, and in this case Elmax and XHP both get it done really well... even though they're very different chemically. :) What they have in common is very high quality/cleanliness and very fine structure... that's good for any steel, and among other things, it allows the engineers (and knifemakers) to decide how much carbide content they want, without messing up the toughness.

fmajor007 said:
As always, there seems to be a trade-off with materials and ELMAX (and as I've just learned CTS-XHP) does a superb job at striking a balance (along with M390, et al).
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If you keep looking at alloys in terms of how balanced they are, you will find success. :thumbup:

(PS I hear very good things about M390 as well, and it indeed appears to belong in the same class as Elmax and XHP... but I haven't worked with it yet so I can't really comment)
 
james terrio said:
Not a "political answer" at all, that's my honest opinion.
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LOL - I was completely kidding about political-ness - I knew your intent and context :D. I appreciate your response by addressing the essence of my question and recommending both choices as appropriate for the task(s) of bushcraft.

james terrio said:
There's more than one way to skin a cat, and in this case Elmax and XHP both get it done really well... even though they're very different chemically. :) What they have in common is very high quality/cleanliness and very fine structure... that's good for any steel, and among other things, it allows the engineers (and knifemakers) to decide how much carbide content they want, without messing up the toughness.
Click to expand...

Precisely the type of answer I was hoping for - especially "even though they're very different chemically". The internet keyboard commandos who merely read about metallurgy won't *know* the actual handling characteristics of the "different chemically" steels simply because they've not personally *used* them. I'm a user, not a theorist.

I hope EnZo does decide to offer ELMAX for their Trapper - I'll be the 1st in line to buy a blank.
 
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