Another plane iron durability test

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24 Aug 2015
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Last year, I tested a bunch of plane irons. A few simple irons and then everything from A2 to CPM M4. M4 ended up lasting the longest, and V11 was just on its heels. I've found since that if you're planing rough wood, V11 and the alloy that it's made of (or suspected, I don't know for sure) is high hardness for stainless but not high toughness. It's abrasion resistant when honing and grinds slowly, so it's fairly easy on something like a jointer to end up never having all of the damage out of an iron unless you spend proportional time sharpening (or more) and using maybe a sharpening media you don't want to.

So I've gone back to O1 and the likes (or simpler) for all pre-smoothing work, and to be truthful, I've not used the V11 alloy (my make or LV's) for much of this year as I've made three projects out of "trash wood" that has knots and such. It's easier to use a soft iron that has good toughness and can be refreshed fast on one stone and the buffer.

That leads me back to testing somethings that I'd gotten before V11 and a couple after:
- 1084 steel
- 1095 steel
- 52100
- AEB-L (a fine grained stainless that was developed for razor blades and that I threw in at the last second here after being told by a metallurgist that I might like it. It's not a PM like V11, it doesn't have that high of carbon like V11, but it has the finest grain structure of any stainless that I'm aware of - finer than any of the stainless PMs). It also has a reputation with small carbides of being tough and sharpening more like a carbon steel. I'm in
- 01 - the same iron I used in my prior test, which helps me make some connections

1084 and 1095 are two different plain steels used for two different reasons (1084 doesn't develop much for free carbides and thus stays tough. Lack of carbides means it wears a little faster, but it sharpens easily at any given hardness). 1095 us sort of the plainest 1% carbon steel you can find, but I've found out that it's too plain and a couple of the alloying elements that make a slightly less simple steel get full hardness more easily are a good idea. small amounts of elements can also improve toughness. My guess is that the really simple high carbon steels wiht a little bit of additives are what's in files, which have big demands on their teeth and are really high hardness. I just have no idea what's actually used in files and i'm fairly sure that the assumption that it's 1095 is wrong because they don't harden the same.

52100 is a steel regarded as tough at high hardness and favored in the knife world over 01 for several reasons. Its structure (some alloying elements, but still pretty plain) suggests that it should last about like 01.

The test is in plain maple, 200 feet against the grain (which is harder on an edge) and then the rest with the grain.

the results that I got are as follows:
1084 steel - 997 feet

1095 steel - 836 feet (toughness problems, and nicking which shortened edge life but they wore off by the end of the test and the edge looked wonderful - I think a few extra degrees or some buffing of the tip to remove the weak apex would make it a better peformer, but why when 1084 works so well and is easier to get right hardening because the grain structure never really degrades in simple heat treating.

52100 - 1235 feet (lovely, hard crisp edge and nearly no chipping even against the grain with a fresh edge

O1 - 1231 feet (almost indistinguishable vs. the 52100 iron, though the small amount of alloying in each is not the same - the result is similar. O1 is probably a little easier to heat treat as it's designed to harden deeper in large items)

AEB-L - two tests averaged 2000 feet. This is a surprise. AEB-L (also sold by sandvik as 13c26) has less than 0.7% carbon and has about 13% chromium and a few other additives. It works out that the combination leaves no large free carbides. I expected the low carbon to make the edge tricky and once I figured out how to harden and temper it in open atmosphere (it can do better when commercially done, but would need specific temperature cycling and cryo treatment). It just keeps cutting, almost as long as V11, but the steel cost for AEB-L is about a fifth of the cost of V11's base stock and it's available in more sizes. It also sharpens easily on india stones and oilstones and has great toughness.

In order to harden and temper it, though, one needs to be able to get close to 2000 degrees but not go beyond (higher than that and it will lose hardness rather than gain it unless you can dip it in liquid nitrogen (if you can do that, it can get up to 65/66 initial hardness, which gives you a lot of room to temper it back). The high temperature is needed as it's not PM and chromium will not dissolve into the solution at lower temperatures. The rest of the steel will harden, but the chromium will just chip right off of the edge. BTDT on the first try.

I can tolerate heating it (by color) in the temperature range for about 3 minutes before I can't stand sitting and looking at it longer, and don't want to have more carbon float off into the atmosphere than needed. That seems to be enough, and my sample which I thought was soft at first (due to the decarb layer) is now in the toaster oven tempering back a little bit as after a few sharpenings, i'd like it to be a bit easier/freer grinding, but at this point, it is wearing smooth and even like a carbon steel (albeit a hard one) and lasting a very long time (unlike A2, which grinds much more slowly than carbon steel but offers longevity only slightly longer and a trash edge during that longer period).

I had a couple of failed tests, and this was overall a mini-test (only about 9000 feet of total planing vs. closer to 40-50k in the original test.

What are the chances that AEB-L will ever make it into a commercial plane iron? Pretty low, I think. It's probably been around 50 years already and you can't just dip it in oil to quench and then dip it in salt or high temp oil to temper like you can with O1. And so far, it's a bit less stable (warps a little bit) in quench vs. A2 which has great dimensional stability.

In short, it's better for us than A2, but A2 is probably easier for makers to work with (and their contracted heat treat for the makers who send stuff off).

I do think also that AEB-L has the potential (unlike V11 for me) to do the whole range of work and have nicking removed just in the process of regular honing and grinding, which means no working late in a project finish planing a surface only to see a shaving still splitting right after a brisk sharpening session.

Too on top of that, for someone who likes really easy to sharpen and good toughness, 1084 performed very respectably. It sharpens like butter, even at relatively high hardness, because there's nothing in it to resist the stones.
Pictures of 1084 at 433 feet, and then at the test end (997 feet)


(lovely smooth edge - the lines going parallel to the edge are just paraffin wax that didn't wipe off completely).
52100 at 433 feet:

at the end of the test (1235 feet)
AEB-L looked a little different - the first test was outright failure, so I rehardened it. Heres the first version at 433 feet (I couldn't keep the edge together and the sharpening scratches were deep - I now think a lot of this was due to a decarb layer, because it occurred again after the second heat treat)


After the end of the first test (which went over 2000 feet)

Nice even edge, but why doesn't it have the same scooped shape? I don't know, so I did another test.

at 1950 feet, I gave up, the iron probably had a little more left in it. Maybe another couple of hundred feet, but planing for a long time with an almost dull iron is miserable.

Same look of the edge being a little more rounded at the tip and no scoop.

I have seen the results of a knife guy testing AEB-L with test cards (they're cardstock impregnated with sand more or less to accelerate wearing out a knife edge). It lasts longer than carbon steel in all of those tests (any carbon steel, including stuff like japanese blue super, which really doesn't last much longer than O1 or anything else - he covers that in his tests, too, with etches of the grain structure). These results are a higher ratio vs. the knife machine test, though. The machine tests found AEB-L to last up to 1.5 times longer than something like O1, but my ratios are more like 1.6 or 1.7 and there's not a great chance that I'm doing an optimal job heat treating any stainless in an open atmosphere.
More about the AEB-L Alloy - I'm smitten as the bits about stainless that aren't like carbon steels are usually the turnoff to me.


AEB-L looks like carbon steel under the microscope. I would never have believed that a 0.7% carbon steel could attain high hardness and have decent toughness.

And, aside from being a little bit more difficult to handle in the open atmosphere, it's very inexpensive (if I spread shipping across bar stock, it's about $9 worth of steel - about the same price as 52100 and cheaper than ground O1).
Very interesting stuff, I will try to see if I can find that AEB-L to give it a try myself. Do you happen to know which alloy is V11, or its composition?
Suspected based on a post on sawmill creek to be cts xhp. I've made half a dozen irons now from cts xhp, and they feel identical and wear the same (twice as long as 01) in clean wood.

Xhp makes an iron well if you can get 1900 degrees f of heat quickly and quench.

All of these temper in temperatures that can be reached in a kitchen oven.
I've only been able to get xhp from one supplier- sb specialty metals in the USA. It's expensive and only in .094 ground or .103, but that happens to be a good thickness for a plane iron.
Yesterday I made a small iron for one of my favourite block planes, did the heat treat and I must say I'm liking it a lot. I wrapped the iron in stainless steel foil to prevent decarobonisation and the iron came out looking very nice. Sharpening was quick and effective.
Ready for testing:
Nice! I'm glad to see someone else giving something unusual a shot!
David-what are your heat treat and draw parameter?

For XHP, I heat to temperature color match (around 1900F), hold only for a short period of time once color is obtained just to look the iron over and make sure it's uniformly heated, and then quench in oil, then two tempers at 400F.

For AEB-L, same thing, except the steel has to be held at color to melt at least some of the chromium into solution. I did this for about 3 minutes, which led to a decarb layer. I tried the same thing as I do for XHP, but the iron chipped and seemed a little bit underhardened (that may have been decarb). The second attempt, I held at temperature and oil quenched and then tempered to about 325 degrees initially, but the result was way too hard (surprisingly - by Larrin Thomas's chart, I'd have expected to miss the mark a little bit and then make up for it with lower tempering). I've tempered now up to very light straw and the iron still seems a little harder than what I was aiming for (which would be a very easy sharpening stainless iron).

It'll be worth getting some commercially HT at some point to compare, maybe.

(My temp/color match is a guess at this point, guessed only by success with XHP in terms of getting a good quench and temper that makes an iron that feels exactly like LV's and matches same in a test).

You want me to cut one and send it to you to analyze? I can't possibly be that accurate doing this by eye, but the results have been surprisingly usable. Commercial HT sort of ruins the jones of making a $10 stainless iron with consumables included in that cost.
We’d be tossing good dollars after bad, until we have fully controlled procedures. what Measures are you using to control de carb?
Nothing - I grind it off after the fact. hardness is subsequently graded by grinding and how easily an iron hones on india in combination with behavior of the burr and how strong the edge is (how well the initial fine edge holds). My true target is something that hones well on an india stone like carbon steel does, but the iron is a bit too hard for that.

I think if we were shooting for much higher targets, like trying to make knife blades that are 10 degrees per side (or making a straight razor), then really optimizing things would start to count, as we'd need perfect dispersion, the appropriate hardness for strength and toughness to go along with it. But with a plane iron that's beveled to a hair over 30 degrees, the bar isn't that high. Durability in feet planed is the second bar, and AEB-L even just with decarb ground off is surprisingly good. Almost as good as XHP, but at about 1/5th or 1/6th of the cost, with better toughness and if commercial HT warrants it, at least as high of hardness potential. It shares one other tendency of XHP - it doesn't spark much and requires a light touch on a grinder.

The one very noticeable thing with it as flat stock unlike XHP, though, is that it files and hacksaws and cuts (even with a dry power bandsaw) somewhat similar to carbon steel. Any part of XHP gets hot, whether by drill bit or bandsaw blade, and it instantly hardens. It takes me about 1 hour to make an iron with AEB-L or carbon steel (by hand/drill press, filing, etc) and 2 with XHP - XHP requires more attention to avoiding heating any part of it, and then once you're into the hand filing part, it's really icy with files.

I see AEB-L as a good option for LN if they can't find someone who will deal with the warping of O1, except that it's just better than A2 all around (finer grain, longer wearing, cheaper) except perhaps with warping - I haven't done the more traditional plate quench with AEB-L as I will sneak on generating higher hardness with air hardenable steel by using an oil quench and then just deal with the warping (XHP will give you an extra point or so with oil quench vs. plate quench, at least according to carpenter's data sheet).
You gave me some stuff to ponder, Dave. Heat treat and draw is possible to make one steel act as another, for example a D2 as A2 or S7. Now, I can also take parts I make (my employees), from conventional powder metal and spot heat treat portions, and I would imagine the same process (it was a wrought process), might do some interesting things on a plane blade, though there would be a narrow range between useable/desirable and ending with a blade that shatters like glass.

I suppose we could take a stack of blades (flat to flat), to add mass and spot heat treat the work edge. Warping and de-carb could be controlled, with piece to piece variability almost eliminated (think production blade making).

As I said at the beginnin, I got some pondering to do!

Yes on the HT. One of the interesting tricks with japanese tools is tempering "swedish" steel tools (assab k120, etc) soft and then having people rave about how easily they sharpen because of the "easy sharpening swedish steel". They're just softer!! Assab is 1.2% steel. White steel is generally 1.2% steel, and people hate softer japanese tools (regarded as cheap), but if you create a myth that the swedish steel is softer when it's just tempered softer, then it's deemed as a lovely option.

I can take a file (which I know is fairly close to plain) and make it almost unsharpenable even on an india stone. It's harder to sharpen than an A2 iron at LN spec by a lot, or you or I could take some of T series high speed steels and temper them soft and they sharpen on natural stones. The tungsten carbide probably doesn't, but the tool does. I have a "revilo" high speed steel iron in an infill from eons ago and I waited with anticipation to get it to see how people could possibly have sharpened it. ......It's high speed steel, but it's tempered softer.

I don't want to overestimate my ability to get a good result heat treating by eye - I can get an acceptable result, but I don't play with anything that requires more than about 1950 degrees, nor any of the dual temper range steels like 3V, etc. It's got to be easy as a poorly hardened 3V iron would be worse than satisfactory AEB-L.

Given that I surprisingly got high hardness with AEB-L, it's likely that analysis would find that I came up short on toughness vs. an iron done by commercial service.

Am I gathering correctly that you'd spot heat AEB-L irons in a stack to prevent decarb and then snag them out of the stack and quench them?

I think probably by next year (got a couple of strong grinders this year and a 5k ft/min belt grinder), I'll go to the trouble of getting a proper furnace, but we'll see how the year goes.

I do believe there is probably a market for a fine grained easy sharpening stainless that still wears pretty long.