Heat Treatment - Crystal Weaving Foundation

For this M2 blade (cwf ht 1.0), I was looking for 64rc w/o enter into secondary temper temperature range (i.e. above 600F, where CrC precipt and coarsening and loss of corrosion resistance+toughness). I want to refine/tailor ht params to hit good hardness and toughness with low temper temp range. When time permits, I will cwf ht 1.5 (grain refine + elem gradient + cr partition) more M2 blades. I would like to see damage mode = larger ripple/bent prior to fracture/chip.
 
I'll be looking forward to your results with M2 and how it compares to the other steels. :thumbup:
 
Using my latest ht - Niolox/SB1 closely matched hrc however exceeded in wear resistant than projected.

Edge after induced damage by cross grain batoning Katalox wood
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Apex of this niolox blade will micro-roll (barely visible) and fairly large ripple (micro to macro) and eventually chip when push beyond plastic range.

Micro-roll is something I've been chasing. It's a good mitigation mechanism to minimize apex damage when encounter destructive impact forces (compressive & lateral). Current experiment M4, D2, Aebl, 52100, W2, etc... blades are also exhibiting this micro-roll.
 
Luong, Do you think those large, half-moon chips at the left were caused by lateral stresses on the edge, caused maybe by the cross-grain deflecting hard forward chops under power? That's been my experience from chopping branches.
 
Yes by a massive lateral bowl bend due to edge steering. The cut look like scooped by a spoon. I heard 2 ticks as batoning harder trying to cut through 1" square katalox - almost made it. Cross section thick of this chip is about 0.021". I can chop into katalox - all day - with this knife as hard as I can - due to low momentum (4" blade, ~4 oz blade) best cross grain penetration is about 1/4" deep. A 10" chopper with this thin geometry would suffer this type of half-moon chips. Even with a chopper, it down right difficult to chop through 1" square katalox. 20 dps edge chopper probably won't go 1/2" deep.

Worse technique or mistrike when chopping very dense & hard wood, when edge enter at ~45* and about 1/8-1/4" deep and the blade just flip. It's enter and pry. Easily reproduce by hold a board or 1.5" square of katalox or AfricanBlackwood at 45*, chop down and turn palm up at impact. So edge dug in a little bit, then blade turn over into a pry = trying to lateral break the edge with a wood plier. This doesn't occurs much when chopping softer woods because either penetration is deeper (onto thicker part of blade) and or successful pry-out.

Twindog said:
Luong, Do you think those large, half-moon chips at the left were caused by lateral stresses on the edge, caused maybe by the cross-grain deflecting hard forward chops under power? That's been my experience from chopping branches.
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bluntcut said:
Yes by a massive lateral bowl bend due to edge steering. The cut look like scooped by a spoon. I heard 2 ticks as batoning harder trying to cut through 1" square katalox - almost made it. Cross section thick of this chip is about 0.021". I can chop into katalox - all day - with this knife as hard as I can - due to low momentum (4" blade, ~4 oz blade) best cross grain penetration is about 1/4" deep. A 10" chopper with this thin geometry would suffer this type of half-moon chips. Even with a chopper, it down right difficult to chop through 1" square katalox. 20 dps edge chopper probably won't go 1/2" deep.

Worse technique or mistrike when chopping very dense & hard wood, when edge enter at ~45* and about 1/8-1/4" deep and the blade just flip. It's enter and pry. Easily reproduce by hold a board or 1.5" square of katalox or AfricanBlackwood at 45*, chop down and turn palm up at impact. So edge dug in a little bit, then blade turn over into a pry = trying to lateral break the edge with a wood plier. This doesn't occurs much when chopping softer woods because either penetration is deeper (onto thicker part of blade) and or successful pry-out.
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Luong, thanks for explaining. Is this what CWF try to achieve? A good chopping tools that bite deep and able to 'scoop' out the chips (wood not steel) that let the user finish work sooner?
 
Scoop part is the trail/evidence of edge being steered so severely until resulted in half-moon chips in this case. Curvature of the bowl/spoon indicates magnitude of flex (and bent) before fractured. I will try to remember to take a snapshot of this next time.

My discussion will be in context of BCMW 66rc M4 (which is close to Vanadis4E, where CPM 4V would be almost identical in composition). Fairly safe to extrapolate M4 has similar bending strength as Vanadis4E.

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Which coincide with Crucible listed M4 bending strength between 5000-5130 MPa - http://www.crucible.com/eselector/prodbyapp/highspeed/cpm4hch.html

66rc from chart above - 4800 MPa bending strength (avg); 1mm Plastic deformation; 4mm deflection.

It means - an edge can deflect/flex to some low amount and combine with very little plasticity, it would yield in fracture/chip.

I mentioned (in prev post) about micro-rolls and ripples edge for M4 (at 66rc my latest ht). But this contradict/dis-agree with the published chart above. In order to roll (at any scope level), microstructure requires quite a bit of combined ferrite & RA to attain plasticity (allow slip and slide within matrix). Ripple requires less plasticity than roll. So what's going on here?

In my pursuit (via whatever right/wrong understanding of metallurgy)... At 66rc matrix grain will behaves as a non-yielding particle. Yielding/plasticity limited to grain boundaries (GB). By increase GB, so will plasticity. Aha, this echo my repeated quests of applying grain refinement. Again I link - https://en.wikipedia.org/wiki/Grain_boundary_strengthening

Unless there are gross errors in my tests... microroll (and or extensive ripple) only possible when grain size is small enough and grain boundaries are clean (low misalign angle and dislocation and high cohesion).

In a well established field - such as metallurgy, a gain/improvement of 10-40% would be extraordinary. However this linear gain is a minor variable in edge stability in compare to cubic response of geometry. e.g 18 dps is 73% stronger to 15 dps by steel volume - as you can see how a small change of dps would drown out 10-40% gain of microstructure. Otoh, if BCMW 16dps has same strength as std ht 18dps... I will chase 15dps :p

Chris "Anagarika";17034001 said:
Luong, thanks for explaining. Is this what CWF try to achieve? A good chopping tools that bite deep and able to 'scoop' out the chips (wood not steel) that let the user finish work sooner?
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Spent my weekend on HT 2.0 - grain refinement and interface optimization.

D2 blades - destruction tested. D2 has coarse primary carbides, so it would need a good amt(TBD) of ferrite (and or RA) in order to arrest/prevent crack nucleation and propagation. There blades are very strong and has good sub-micron edge stability in pressure cutting and quite stiff enable good penetration into hard material. It fractures/chips when go past yield point.
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A drill bit broken surface
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Edit to stash thought outines:
Unyielding particle/volume at microstructure and related to hrc.
Yielding Unit and cascading YUs (CYU).
Blade steel attributes by design for intended uses in relation to YU & CYU.
 
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HT 2.0: Cruwear (cast/ingot steel, not PM) vs M2. IMO - it's a draw, even though Cruwear shows a slightly larger chip(from 5-6 chops). At ~65.25rc cruwear ripple (plasticity) a little less than m2. If cruwear at same 64.5rc as M2 - I think, cruwear will pull ahead of M2 because it would still be slightly stronger than M2. Edge stability of both blades are very high - they kept keen edge even chop cross grain into a block of dried katalox. I will take a peek of both under microscope to compare carbide size of these 2 against M4 (M4 MC ~1.5um dia).

* With my ht 1x to 2.0 - M2 warp quite a bit (even with an unground blank).

biA1OC9.jpg


edit to update: M2 carbides look finer than cruwear (as expected anyway) - est in 500-750nm range. Did a wide scanned - I did spotted a ~1.5-2um dia carbide in cruwear. Also saw something look like fine grain boundaries for cruwear. I might polish & nital etch blades for taking a closer look.
 
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Interesting cruwear did that well. I figured it would fracture or permanently deform a little before m2. But then, all my comparisons of both steels, except your z-wear superquench, are with conventional ht. Thanks!
 
Superquench has limited usefulness in steels with high hardening temperature (above 1600F). Limited because I wasn't about to refine grain for those steels, so SQ ended up with more strength but with more/less same grain size, boundaries and particle interfaces. HT 2.0 built on top of (actually, in conjunction) CWF HT 1.0, which refine grain; optimize grain boundaries and particle interfaces.

From quite a bit of testing M4. I chose cruwear (cast) because it sort of a little more wear & corrosion resistances to M2. Cruwear peak hrc around 67 (similar to M2). I am looking for long sustain high keenness, so far in this batch cruwear performed better than M2. However M2 is slightly handicapped by hardening temperature was at the low end - thus some carbides are a little bit large (2-3um), in turn degrade high keenness apex.

I only have nital etchant so cruwear didn't delineate much in picture but actually can see details fairly well in visual. Anyway, pic below show est M2 grain dia below 5um. Cruwear grain seems finer. M4 as reference.

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jpm2 said:
Interesting cruwear did that well. I figured it would fracture or permanently deform a little before m2. But then, all my comparisons of both steels, except your z-wear superquench, are with conventional ht. Thanks!
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I lowered the hardness of Cruwear to 65rc and M2 to 64rc. Quite certain, I can tune M2 ht params to 65rc (with ~0.5% carbide volume lower - yeah undetectable) with same capability as this M2 64rc.

When chopping (especially cross-grain into hardwoods) with low sharpening angle and keen/sharp apex, damage will take place - this is an instance of how much:

fifl2UE.jpg
 
I would say by those pictures, that they were not equal, but might be my untrained eye.
How would your M4 or 10V HT 2.0 compare to those?
 
Sorry, I should cut off the lower half of pic because the cruwear suffered a few nasty deflected chops in those area - hence large ripples and flattened.

At this level of sharpeness and low angle - (go by memory, maybe snap a few pics next time) M4/65rc will has a little wider apex radius (~20um) and no ripple. 10V 68rc ~25-50um and no ripple for sure.

Hopefully some body out there would try this test (with any steels & hardness) and share results. Give a few full fast chops African Blackwood (or substitute with Desert Iron Wood) with big or tiny pocket knives. Compare result edge with std 16um aluminum foil. :thumbup:

jpm2 said:
I would say by those pictures, that they were not equal, but might be my untrained eye.
How would your M4 or 10V HT 2.0 compare to those?
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Great work and testing Luong! In the Nital etchant pics, does the yellow or the red show the carbides?

Btw my 10v blade at 68rc is holding up well! It seems to hold an edge that will slice paper for a long time, but loses keenness fairly normally (when cutting cardboard compared to other steels). Does this have to do with the carbide size in 10v, and if so, what size are they?

I've hacked at a few green limbs around the house w/ no edge deformation yet (remember this is ground super thin, .007-.008 at 15 dps) so it's holding up surprisingly well so far. Been carrying it non-stop since I got it put back together.

I've gotta finish the M4 and AEB-L blades out for testing still... running short on time lately

already posted this elsewhere but for a visual for others:

i-nhQWQMr-X2.jpg
 
There, look there, that nice looking knife appears again... Maybe it's real :p:cool:

This folder edge has a recurve edge profile, so medium to high pressure cutting will tend to focus/converge to push cutting. Where carbides only able to shield certain % of the apex, the rest wear on the matrix. So if other blades with lower carbide volume steels have this same edge profile and even same hardness, they would loose the edge faster than wharncliffe and belly profile blades. Hence in this context, this 10V 68.5rc performed nifty well... hahaha unless my assertion about edge profile & your-cutting-technique is totally off.

Your M4 blade (diff edge profile) should has better cardboard cutting performance than 10V - when cut normally but lower perf when push cut cardboard.

razor-edge-knives said:
Great work and testing Luong! In the Nital etchant pics, does the yellow or the red show the carbides?

Btw my 10v blade at 68rc is holding up well! It seems to hold an edge that will slice paper for a long time, but loses keenness fairly normally (when cutting cardboard compared to other steels). Does this have to do with the carbide size in 10v, and if so, what size are they?

I've hacked at a few green limbs around the house w/ no edge deformation yet (remember this is ground super thin, .007-.008 at 15 dps) so it's holding up surprisingly well so far. Been carrying it non-stop since I got it put back together.

I've gotta finish the M4 and AEB-L blades out for testing still... running short on time lately

already posted this elsewhere but for a visual for others:

i-nhQWQMr-X2.jpg
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I just collected a pseudo bending tests for 4 of my experimental blades. *note - break is at vise pinch point, so bending curvature is quite short - actual bending length probably can bend a more than recorded. E.g. Pic at bottom - the front 30mm represent the material bending limits. Ratio using that = ~ 30/2.67 = ~ 11.24. Which is a very tight arc.

Bending length 8cm.

3V 62rc (ht 1.5) 0.105"/2.67mm thick
Elmax 63rc 0.100"/2.54mm thick
D2 61rc 0.110"/2.79mm thick
D2 66rc 0.120"/3.05mm thick

[video=youtube_share;mOcUIgGHQeI]http://youtu.be/mOcUIgGHQeI[/video]

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* NOTICE - although I've tested many ht 1.5 blades in steels: 3V, aebl,D2, M4, 10V, etc..., due to gradient elements distribution - high likeliness of errors/mistakes. *

This (post-ht ground) 3V 62rc ht 1.5 exhibits excessive ductility at the edge, maybe hardness is lower there. But that would contradict with my whittle tests (AB and bone) since the edge passed those tests.

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Why this stuff show up now? BCMW is at ht 2.0 (grain size; grain boundary; particle interface optimization; excludes element gradient), so logical progression to assess 1.5 vs 2.1x(include elem grad).

It is understandable, my concepts are very unconventional and possibly un-metallurgical.

In nature, Interface Optimization occurs naturally(yeah) via processes to reduce potential energy. e.g. Rocks tendency to settle at low points rather ridges or saddle points. In a steel matrix, gap/porosity reflect level of potential energy (dislocation). Here is a sketch of it. HT 2.0 in practice/reality - With limited/sufficient data, I detected performance gain. But not easily to quantify due to lacked of concrete qualifications - aka unproven claimed.

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Luong,

I cringed a lot watching those good blades being broken :eek:
Interesting thought about the 3V that passed whittle bones test but still have such ductility... I am not sure though that my head won't cracked trying to understand :o
 
HT tuning for Elem Grad is very time consuming. I had to use the microscope to verify carbide size+density for various depth into cross section. At this point, benefit/cost ratio is too low to apply this technique, especially for non-chopping knives. Sword/machete/thin-chopper are more appropriate for it. Almost forget - grinding for this is mostly post ht, which isn't easy nor cheap.

I've a few M4 with ht 1.5 64+rc blades (and a chopper) - they exhibit a lot more ductility than my other M4 ht 1.2 & 2.0 blades.

Older posts ^ (months ago) - I discussed about elem grad concept. I am crazy today as months ago :p

Chris "Anagarika";17072866 said:
Luong,

I cringed a lot watching those good blades being broken :eek:
Interesting thought about the 3V that passed whittle bones test but still have such ductility... I am not sure though that my head won't cracked trying to understand :o
Click to expand...
 
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