Heat Treatment - Crystal Weaving Foundation

Very nice Luong! Question... how would rex 121 perform at 71rc do you suppose?

Those m390/20cv numbers are impressive... as far as I'm aware conventional ht is max of 61-62rc!
 
razor-edge-knives said:
Very nice Luong! Question... how would rex 121 perform at 71rc do you suppose?
Those m390/20cv numbers are impressive... as far as I'm aware conventional ht is max of 61-62rc!
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Rex121 71rc should be fine as slicer and ain't frail facing edge impact.

Brian77 said:
I hope to test 20cv at this Hardness
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I've a handful of 20cv blades with ht 2.5 but been collecting dust... except for 1 faced duty call this evening... If you like, I can send this blade *as tested* to you for testing (optional review - might as well eh!). Send back when done or arrange to keep.

** duty call for rex & 20 - unfortunately I sharpened these 2 test blades below 15dps**

BCMW HT 2.5

CPM Rex 121, 71rc
Sharpened with diamond plates: 400, 600, 3K (equiv to dmt x,c,e)
28 degrees inclusive, 0.009" behind edge thick

CPM 20CV, 65+rc
Sharpened with diamond plates: 400, 600, 3K (equiv to dmt x,c,e)
26-27 degrees inclusive, 0.010" behind edge thick

Cut: rope
Whittle: rosewood, bone
Chop: rosewood, bone

Result: rex - microchips under 22x loupe. 20cv - visible ripples, microchips(bigger than rex) under 22x loupe.

 
Got reinforcement niolox ;) Yup, excellent price & fast shipping. For this batch - David Haley custom ground 1.7mm thick niolox for me. He did 1000mm cut length for me last time. These sheets are near precision ground, so easy and save time to make blanks.

5RCGXeh.jpg


Per 20CV at 65rc: From the chart 20cv/M309 has ~ 21 vol% of uElem (unbounded elements) and as high as S110V uElem. 20CV 66rc with this much uElemVol% has excess matrix dislocation/stress, therefore lower 0.5-1rc to ease/relief some of dislocation to keep edge stability align with other high freeCr% steels at & near peak hrc. You can see niolox/aebl/nitro-v ~14-15% are best among hardened stainless steels. Excluded cts-xhp freeCr% likely below 10% in spite of it low uElem.

ht 2.5 10V at 69rc vs maxamet 67rc - based only ulem%, I project they have similar edge stability even though 10v has higher carbide volume and 2rc higher.
 
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razor-edge-knives said:
...
Those m390/20cv numbers are impressive... as far as I'm aware conventional ht is max of 61-62rc!
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Conventional/std ht for 20cv/m390 HRC peak around 64rc. Edge stability at peak hrc is brittle because of high dislocation and RA - assertion based on my reasons/interpretation below this pic.

Lh44ZZl.jpg


i. & iii. are 2 hrc peaks. Where RA% goes to zero at iii. So iv. working hrc edge is more stable than ii. because at ii. has RA% and higher dislocation (main reason for RA% to be there). Thus mfg recommended iv., to a point not even publish temper/hrc for temperature below 200C/390F.

For curve of 390 ht with subzero: I guess/loosely-correlate aust 1150c to 35% of RA at room temp prior to sub zero.

i. 2 rc higher than ht w/o subzero, maybe SZ reduced RA to ~10-15%

ii. this is commonly use temperature for low temper range. These p0ints on both curves (SZ and none) are still highly stress/dislocation thereby still a bunch of RA%.

iii. RA to martensite conversion and carbide coarsening produced net gain in hrc relative to ii.

iv. matrix precipitation faster than carbide coarsening, so hrc dropped and when ferrite% is sufficent (dutility), voi'la = mfg suggested working range. Most carbides coarsening due to Cr alloyed with precipitated carbon, exactly mfg stated loss of corrosion resistant at this range of temper temp.

**** BCMW HT 2.5 plausibility ****

20cv peak 66rc hrc at temperature below 200C, which implies this matrix has low dislocation thereby very low RA. *note: RA hardness is similar to ferrite/iron because both FCC & BCC are cubic structure, where martensite has BCT shape = steel.

HT 2.5 edge at near peak hrc actually more stable and stronger than ii. and iv. While at same corrosion resistant as ii.
 
I tested edge retention of niolox 64rc ht 2.4. Started with ~dmt E edge, slice phonebook loudly. 4 hrs of hacked palm fronds from 5 trees and then 3.5chops per stem + 2 slices on fan/leave... Edge afterward noisy and 3 catches slice phonebook and would easy to make fuzz feather to printer paper. Edge still catches thumb nail. iirc 52100/w2 edges were still sharp but lost their bite after couple hrs of hacking dusty palm fronds.

1428HZl.jpg
 
Thanks. It wasn't too tiring, when chopping at certain sustainable/exercise pace, it's a substitute exercise while I need to wait a few more days for stitches to heal before swim again. A Niolox 7" zero ground petty gave my finger a hard kiss. Prior to this event, I was going to procrastinate by doing easy grinding work a few 10V knives. Hard to persuade/understand but niolox 0.8%C 65.5rc is harder to grind than 69rc 10v 2.45%C. Grind rate at 80 grits about the same but 120+ grit, belt start to burnish for niolox after belt ceramic lost 5% peak sharpness vs 10-15% for 10v.

This test help to erase/ease doubt in my mind, whether ht 2.4 & 2.5 edges actually good or just a want/wish-to-be-so/dreaming. Still I need to mindful (take into account), my usage technique is probably toward high skills users, whereas less skillful users would put a lot more lateral forces on the edge.

Chris "Anagarika" said:
Luong,

Niolox is your favorite nowadays :thumbsup:

Marathon chopping must be tiring! :eek:
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Luong,

From what I understand, the carbides are well distributed on Niolox causing the belt wear. It's another proof for 2.5 as huge jump. :thumbsup:

Foofie,

Thanks for arranging the pass around. I'm outside US so can't participate. Besides my use case doesn't justify Luong's CWF 2.5. :oops:
Agree S30V is good candidate for people to try & compare the performance! Kudos and wish all good time testing!
 
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foofie :thumbsup:

S30V from Crucible's Literature - http://www.crucible.com/PDFs/DataSheets2010/dsS30Vv1 2010.pdf
has peak(as-quenched) hardness at 64rc. With a quick google search, there shouldn't be any working S30V knives with hardness higher than 63rc because steel matrix (of standard ht) at this hardness is likely be untempered, hence very brittle.

For BCMW, S30V didn't joined rank of other stainless steels until HT 2.5, prior to that - it was outside looking in. For most stainless steels with 0.8+%Carbon, ht 2.5 yields peak hrc around 66. I expect higher hrc for upper high alloy% steels such as s90v, s110v, s125v, etc but yet to achieve that and possibly additional reasons other than RA% blocked full matrix hardness.

foofie said:
I think I will just leave this here:
https://www.bladeforums.com/threads/passaround-blunt-cut-metal-works-s30v-petty-at-rc65-5.1523992/

Sorry to clutter up your thread, Luong. For those interested in actually trying out HT 2.5, follow the link above.
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I think/speculate, in niolox - very fine + super hard Nb carbides resists/blocks/destroys ceramic cutting tips. Whereas 10V much more MC (primary carbide) with 2+um diameter and lacked of densed very fine & hard carbides, so larger ceramic grits fractured mainly due to collision with MC. I envision niolox has a tight mesh(protected by NbC) which requires much sharper tips to dig, while 10V mesh protected by MC - wider holes mesh - so less sharp grit can dig into matrix. If that is true (well I've plenty of conjectures ;)), then translated mesh size into edge keenness, thereby niolox retains shaving edge longer than those stainless with mostly larger primary carbides.

Chris "Anagarika" said:
Luong,

From what I understand, the carbides are well distributed on Niolox causing the belt wear. It's another proof for 2.5 as huge jump. :thumbsup:
...
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Sometime, one needs actual experience to augment edgeworld's wisdom.

Testing a novelty/straight-razor edge on cpm rex121 at 71rc via ht 2.5.

Sharpened: 7dps up to dmt EE, then stropped on 0.25um diamond powder. est cutting edge (slightly convex) at 8 dps. ~ 0.004"/100um behind edge thick.

MQcIk9B.png


*note on perspective - at 15 dps bevel would be 8 times stronger than 7.5dps due to volume increases at cubic rate.

*the big chip cross-section-thick is about 0.007"/175um.


q6NgupN.jpg
 
From my scientific/math view - curve fitting between points allow easy & fairly accurate interpolation. VS extrapolation/trend/projection error could easily be exponential when far enough from end points. I try to gather data points for rex121 (super high carbide volume, 71rc). I think, it did well - better than expected.

More fun asks - at straight razor edge geometry and any hardness and similar tests - how well will std ht aebl/3v/s7/10v/1095/etc performs?

unwisefool said:
I still don't know what's going on here, but I know I like it!
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I spliced together this max/avg/min carbide volume% = chew or give it a quick glance

7uZQVIh.jpg
 
CPM Rex121 @ 71rc via ht 2.5 - cutting test data point#2.

Sharpened: ~11.5 dps up to dmt EE, then stropped on 0.25um diamond powder at ~8 and 10dps, ~ 0.005"/125um behind edge thick.


Sharpened: ~15 dps up to dmt EE, then stropped on 0.25um diamond powder at 10-12dps, ~ 0.006"/150um behind edge thick.


Sharpened: ~20 dps up to dmt EE, then stropped on 0.25um diamond powder at 15-18dps, ~ 0.005"/125um behind edge thick.

 
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:thumbsup:
Above the edge shoulder(ES) could also be a factor - rex121 71rc 8dps large chip extended above ES to thickness 0.007", just not enough steel to resists bending into the primary (zero ground) bevel to a thin distal tapered spine. Whereas aebl 65.5rc 8dps has larger primary bevel angle - ok, just point out the geometry since aebl only had small edge ripples near apex and far from ES.

Chris "Anagarika" said:
Thanks Luong! Interesting tests and corroborate carbide volume vs BET vs inclusive angle.
:thumbsup:
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1.7mm is an excellent fit for making petty (length & thickness between parer and gyuto) knives and edc slicer as well. I plan to stash more of 1.7mm and hopefully when ready to order - I (with luck) convince David Haley (Pres. of GroundFlatStock.com) for precision ground 1.3mm niolox. Maybe a stainless steel 1.3mm only surface grindable at 2" or 3" wide - can't hurt to ask.

chumaman said:
;) this batch 1.7mm thick niolox is enormous :thumbsup::)
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I will give n690/~vg10 another shot. It has chem specs for kitchen knives at 65+rc via ht 2.5. Too bad, all PM steels have primary carbide diameter larger than 1.5um. I envision something like n690 with 14Cr% and 1.2%Nb might produce carbides diameter less than 500nm(for 99% carbide population), so keen working edge range starts around 600nm - almost razor edge.
 
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