Heat Treatment - Crystal Weaving Foundation

O1 HT 4.0 vs Control/baseline ht - A8Mod and 8670 - chopping test. Edge: Edgepro, 18dps, 600 diamond grit

Dried Eucalyptus: All passed (edges didn't reflected sun light)

African Blackwood:
A8M=dulled and area of minor rolled.
8670=dulled (apex reflects thin band of light and smooth to touch).
O1 = minor ripple (light reflected against edge bevel shows curvature instead of flat)

Dried cow femur bone:
A8M=dulled and minor roll+ripple
8670=dulled and micro roll+ripple
O1=micro roll+ripple

Chop 16D nail:
A8M=crushed and chipped * Surprised to see a very large chip at 60rc :confused: *
8670=crushed/rolled
O1=crushed/rolled

16rrrKZ.jpg


I've HT 4.0 52100 and 80CrV2 with same profile but not ready for testing yet.
 
looks like it deformed so bad it looks like a chip, looks smashed in.

fascinating work Luong

bluntcut said:
O1 HT 4.0 vs Control/baseline ht - A8Mod and 8670 - chopping test. Edge: Edgepro, 18dps, 600 diamond grit

Dried Eucalyptus: All passed (edges didn't reflected sun light)

African Blackwood:
A8M=dulled and area of minor rolled.
8670=dulled (apex reflects thin band of light and smooth to touch).
O1 = minor ripple (light reflected against edge bevel shows curvature instead of flat)

Dried cow femur bone:
A8M=dulled and minor roll+ripple
8670=dulled and micro roll+ripple
O1=micro roll+ripple

Chop 16D nail:
A8M=crushed and chipped * Surprised to see a very large chip at 60rc :confused: *
8670=crushed/rolled
O1=crushed/rolled

16rrrKZ.jpg


I've HT 4.0 52100 and 80CrV2 with same profile but not ready for testing yet.
Click to expand...
 
The O1 and 8670 appear to be the same picture

bluntcut said:
O1 HT 4.0 vs Control/baseline ht - A8Mod and 8670 - chopping test. Edge: Edgepro, 18dps, 600 diamond grit

Dried Eucalyptus: All passed (edges didn't reflected sun light)

African Blackwood:
A8M=dulled and area of minor rolled.
8670=dulled (apex reflects thin band of light and smooth to touch).
O1 = minor ripple (light reflected against edge bevel shows curvature instead of flat)

Dried cow femur bone:
A8M=dulled and minor roll+ripple
8670=dulled and micro roll+ripple
O1=micro roll+ripple

Chop 16D nail:
A8M=crushed and chipped * Surprised to see a very large chip at 60rc :confused: *
8670=crushed/rolled
O1=crushed/rolled

16rrrKZ.jpg


I've HT 4.0 52100 and 80CrV2 with same profile but not ready for testing yet.
Click to expand...
 
My initial thought response was - small chips are precursor to large chips and eventually lead to blade fracture.

Tested A8Mod blade this morning, I made about 6 chops at 16D nail using diff part of edge (avoiding compound damages). First 5 chops were resulted with rolls/dents, so I thought - aha chip from round 1 was an abnormal/exception. Then came chop #6 - well I should be more confidence with my initial thought :)

This std ht A8mod 60rc blade exhibits combination of ductile and brittle behaviors, which reflected edge lacked of strength against hard material and would fracture impact load is large. With this observation, I think, this blade has poor overall toughness.

5D09Drn.jpg


Both O1 65rc and 8670 63rc also tested with 6 chops at 16D nail = both edges were resulted with dent/crushed, no sign of chipping/fracturing.

DeadboxHero said:
Interesting, do you think if stressed enough the a8mod would be the only blade in one piece? Perhaps a low performance edge in favor of overall blade toughness?
Click to expand...

btw - Low hardness 3V 60rc & D2 62rc test blades(same profile as blades above) will be re-ht. Also have a small test blade in ztuff/cd#1 63rc and small 440b 62rc test blade not ready for baton cut 16d nail test yet.
 
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Your findings on A8 modified surprise me. I have two knives in that steel: a rebladed Rukus 610, made by Josh and heat treated by Fredrik Haakonsen; and a Nexus Centurione with a custom heat treat. I also have some Busse knives made in Infi, which is very similar to A8 modified, but I don't know what Busse's heat treat involves.

I've used the Rukus enough to know that the blade has excellent edge stability, although I've not done any abusive testing, which is really the best way to know the steel's limits. I have not tested the Nexus, but there is a video of Italians testing this limited edition heat treat by chopping up rocks, with no damage to the edge or tip. So I can't explain what it going on. Hopefully, this will link to the short (2 minutes) video.


The heat treat from a Google translation doesn't make sense to me, but you might be able to figure it out.

"The steel remained the modified A8, already used on Nexus Caio and Tito. Tempered at 59hrc. For the Centurion, however, more thermal treatments have been made to ensure even greater reliability.
Relaxation treatment performed after the various workings, before the hardening.
The latter, as with the other models, was made in vacuum ovens with forced-off (which, however, ensures a sufficient cooling rate to prevent the precipitation of chromium carbides K1 or K2).
Triple fracture (also in this case as for Nexus Caio and Titus) to exploit the precipitation of secondary carbides, transform all residual austenite into recovered martensites and have optimal eliminations of residual stresses.
The pieces have also been placed in the oven in such a way as to allow homogeneous heating for each specimen."​
 
I am sure surprised by my a8mod test blade. It had ht as posted by AKS (https://www.alphaknifesupply.com/shop/a8-modified-carbon-steel at bottom of page) with 300F tempered to 60rc.

The linked video isn't informative since lacked of edge geometry settings. Baton tip into a clay rock isn't abusive compare to chopping 16D nail. Their 59rc ht is basically standard with some preheating and 3x tempered at ~930F.

My test blade pre-cryo was 59rc and edge was smushy when whittles nail. Around 61+rc post cryo, then tempered to 60rc. So test blade RA% should be less than 2% (expect near zero %). Chips shown/followed weak boundaries, so even if this blade 930F tempered, those weak boundaries persist, even if ductility slightly increase with hardness drop to 59rc. Keep in mind, my test is sample of 1 (for 1 bar of steel with 1 std ht). If(not sure, I want to buy more of this stuff) with a couple more bars of a8mod to test: std vs ht 4.0. I am confidence, ht protocol is a major factor in determine this steel performance, albeit only around 60rc. Maybe(do it if anyone interested to see) I sharpen up the 3v ht 4.0 60rc and chop 16d nail... I am quite certain, 3v 18dps edge would crushed/dent, no chip.

In a way, I am disappointed not having a8mod control/baseline test blade. 8670 63rc blade is excellent baseline/control as comparison reference. Edge stability should encompasses from nano to millimeter depth & width.

Twindog said:
Your findings on A8 modified surprise me. I have two knives in that steel: a rebladed Rukus 610, made by Josh and heat treated by Fredrik Haakonsen; and a Nexus Centurione with a custom heat treat. I also have some Busse knives made in Infi, which is very similar to A8 modified, but I don't know what Busse's heat treat involves.

I've used the Rukus enough to know that the blade has excellent edge stability, although I've not done any abusive testing, which is really the best way to know the steel's limits. I have not tested the Nexus, but there is a video of Italians testing this limited edition heat treat by chopping up rocks, with no damage to the edge or tip. So I can't explain what it going on. Hopefully, this will link to the short (2 minutes) video.


The heat treat from a Google translation doesn't make sense to me, but you might be able to figure it out.

"The steel remained the modified A8, already used on Nexus Caio and Tito. Tempered at 59hrc. For the Centurion, however, more thermal treatments have been made to ensure even greater reliability.
Relaxation treatment performed after the various workings, before the hardening.
The latter, as with the other models, was made in vacuum ovens with forced-off (which, however, ensures a sufficient cooling rate to prevent the precipitation of chromium carbides K1 or K2).
Triple fracture (also in this case as for Nexus Caio and Titus) to exploit the precipitation of secondary carbides, transform all residual austenite into recovered martensites and have optimal eliminations of residual stresses.
The pieces have also been placed in the oven in such a way as to allow homogeneous heating for each specimen."​
Click to expand...
 
No point of keeping this a8mod std ht blade around for control. I will re-ht the a8mod blade to ht 4.0. This way, if a8mod with ht 4.0 performed well, then I can rule out steel issue.
 
Twindog said:
Your findings on A8 modified surprise me. I have two knives in that steel: a rebladed Rukus 610, made by Josh and heat treated by Fredrik Haakonsen; and a Nexus Centurione with a custom heat treat. I also have some Busse knives made in Infi, which is very similar to A8 modified, but I don't know what Busse's heat treat involves.

I've used the Rukus enough to know that the blade has excellent edge stability, although I've not done any abusive testing, which is really the best way to know the steel's limits. I have not tested the Nexus, but there is a video of Italians testing this limited edition heat treat by chopping up rocks, with no damage to the edge or tip. So I can't explain what it going on. Hopefully, this will link to the short (2 minutes) video.


The heat treat from a Google translation doesn't make sense to me, but you might be able to figure it out.

"The steel remained the modified A8, already used on Nexus Caio and Tito. Tempered at 59hrc. For the Centurion, however, more thermal treatments have been made to ensure even greater reliability.
Relaxation treatment performed after the various workings, before the hardening.
The latter, as with the other models, was made in vacuum ovens with forced-off (which, however, ensures a sufficient cooling rate to prevent the precipitation of chromium carbides K1 or K2).
Triple fracture (also in this case as for Nexus Caio and Titus) to exploit the precipitation of secondary carbides, transform all residual austenite into recovered martensites and have optimal eliminations of residual stresses.
The pieces have also been placed in the oven in such a way as to allow homogeneous heating for each specimen."​
Click to expand...
I feel the knife being tested in that video so dang thick it's showing the Geometry more than anything about the steel and HT.
 
bluntcut said:
I am sure surprised by my a8mod test blade. It had ht as posted by AKS (https://www.alphaknifesupply.com/shop/a8-modified-carbon-steel at bottom of page) with 300F tempered to 60rc.

The linked video isn't informative since lacked of edge geometry settings. Baton tip into a clay rock isn't abusive compare to chopping 16D nail. Their 59rc ht is basically standard with some preheating and 3x tempered at ~930F.

My test blade pre-cryo was 59rc and edge was smushy when whittles nail. Around 61+rc post cryo, then tempered to 60rc. So test blade RA% should be less than 2% (expect near zero %). Chips shown/followed weak boundaries, so even if this blade 930F tempered, those weak boundaries persist, even if ductility slightly increase with hardness drop to 59rc. Keep in mind, my test is sample of 1 (for 1 bar of steel with 1 std ht). If(not sure, I want to buy more of this stuff) with a couple more bars of a8mod to test: std vs ht 4.0. I am confidence, ht protocol is a major factor in determine this steel performance, albeit only around 60rc. Maybe(do it if anyone interested to see) I sharpen up the 3v ht 4.0 60rc and chop 16d nail... I am quite certain, 3v 18dps edge would crushed/dent, no chip.

In a way, I am disappointed not having a8mod control/baseline test blade. 8670 63rc blade is excellent baseline/control as comparison reference. Edge stability should encompasses from nano to millimeter depth & width.
Click to expand...
The test knife in A8 had a 300f temper? Was the 8670 a simliar temper too?
 
DeadboxHero said:
I feel the knife being tested in that video so dang thick it's showing the Geometry more than anything about the steel and HT.
Click to expand...

That's a fair point. The geometry is robust, but the steel feels pretty good.

The knife weighs 18 oz. The blade is 7.2 inches. The blade thickness at the rear spine is 0.27 inches. The edge is 24 degrees per side. The edge shoulders are 0.055 inches. So, yes, it's a beast.

Because of the short blade, it's not a good chopper, but it whacked through a sun-hardened Doug fir 2X4 without much effort. After that chopping, the edge would still cleanly slice light notebook paper.

I don't want to test this knife to destruction, but I can usually tell if the steel is not up to snuff (which is why I have destroyed so many knives that just didn't feel right.) This steel feels good.

2v2EdbVfMxAWtWs.jpg

2v2EdbVDyxAWtWs.jpg
 
Yes. Most test blades are tempered around 300F. Except O1 knives technically untempered because none were received temperature above 280F for more than 30 minutes from CWF post cryo heating.
DeadboxHero said:
The test knife in A8 had a 300f temper? Was the 8670 a simliar temper too?
Click to expand...

A8mod edge has 18dps edgepro 600 grit diamond plate, ~ 0.020" BET (edge shoulder).
 
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bluntcut said:
No point of keeping this a8mod std ht blade around for control. I will re-ht the a8mod blade to ht 4.0. This way, if a8mod with ht 4.0 performed well, then I can rule out steel issue.
Click to expand...

This is a really interesting idea ...... testing the same knife, but just redoing it's heat treat. That way I assume you cut out every factor other than the heat treat, and so get a true comparison of the effect of different heat treat protocols on that steel.
 
This blade profile is similar to my 7" chopper (chompers) in 15v and niolox. A heavy short knife is pleasant to chop and actually quite functional for all-purposes kitchen tasks. Perhaps this is why you feel pretty good about this knife rather than the steel.

As for A8Mod (infi cousin) reputation as super tough. In this test a8mod std ht has a huge advantage of - 60rc - much lower hardness than 8670 std ht 63rc and O1 ht 4.0 65rc but it didn't do well. If all test blades at 60rc, data won't be useful since most likely edge of other steels will crushed/dent when chop 16d nail. Sure steels with higher yield strength will have lower magnitude/depth of crushed/dent.

OK need another point of comparison. I put 18dps 0.021" BET on D2 (same blade profile as a8mod and others) HT 4.0 62rc and made 6 chops at 16D nail. Pic is a tad fuzzy due to evening fluttering sunlight but clearly this D2 edge did so much better than a8mod. Under 30x loupe, I can see micro rolls and ripples.

SucT4oJ.jpg


Twindog said:
That's a fair point. The geometry is robust, but the steel feels pretty good.

The knife weighs 18 oz. The blade is 7.2 inches. The blade thickness at the rear spine is 0.27 inches. The edge is 24 degrees per side. The edge shoulders are 0.055 inches. So, yes, it's a beast.

Because of the short blade, it's not a good chopper, but it whacked through a sun-hardened Doug fir 2X4 without much effort. After that chopping, the edge would still cleanly slice light notebook paper.

I don't want to test this knife to destruction, but I can usually tell if the steel is not up to snuff (which is why I have destroyed so many knives that just didn't feel right.) This steel feels good.
Click to expand...
 
Test: Chop & Baton nail with African Blackwood backing. ~18dps, 0.020" BET

440B 62rc ht4 = Chop 6D nail - mostly chipped, some rolled. Baton 16D nail - chipped.

Ztuff/CD1 63rc ht4 = Chop 6D nail - some rolled. Baton 16D nail - some barely visible damage, some rolled, 1 very deep chipped from intentional steered edge.

Test: Break 1-1.5mm edge using a slip joint plier

440B 62rc ht4 = easy breaking off = very brittle
Ztuff/cd1 63rc ht4= very tough, can't seem to grab to snap - jaw kept slid off edge.
A8mod 60rc std ht = loud crunches from chunks of edge breaking off = brittle but less than 440B 62rc.

RFQs charpy impact test @room temperature (machining + impact info/force value) for 3 sets of O1, 2 set of 1095. Most services are offering v-notch (CVN) test.

Prices are high, except for ASTM E23 (10x55x2mm spec) CVN test. I will ask if they are willing to do un-notch 10x55x2.5mm.

Too bad, UCSB ME Dept doesn't maintain a working pendulum toughness tester. No viable numeric (Ft/lbs) translation from dynamic drop to charpy test.

edit: just called charpy test service - they will do astm a370 10x55x2.5 dimension v-notch. Un-notch only offer for cast iron. Most likely I proceed with this vendor.
 
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Sending out samples for Charpy v-notch test

bhe3Br5.jpg


Refining jungle knife profile.
The .120" thick x 2.6" wide profile has very nice balance, especially for pinch-grip at sharpened edge heel.

ch6KHuw.jpg
 
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bluntcut said:
Sending out samples for Charpy v-notch test

bhe3Br5.jpg


Refining jungle knife profile.
The .120" thick x 2.6" wide profile has very nice balance, especially for pinch-grip at sharpened edge heel.

ch6KHuw.jpg
Click to expand...
No wonder why you were so busy and quiet. Processing those samples is no joke lmao.
 
Yep, you are right, making samples is time consuming. Aebl controls/baselines were added to allow cross referencing un-notch (normalize) #s. These samples are not precision prepared, so the testing service will precision machine to exact ASTM dimension. Next test batch, I intent to add 8670 ctrls - improving normalize# relationship between notch & un-notch and different thickness.

DeadboxHero said:
No wonder why you were so busy and quiet. Processing those samples is no joke lmao.
Click to expand...

btw - I ordered some niolox+ (look like Becut equiv), .2419 (O4? equiv) and 1.2519/O7.
 
Few folks here understand the pain.
(Crisp salute)

That niolox+ is disappointing
We already have becut.
More like niolox -

bluntcut said:
Yep, you are right, making samples is time consuming. Aebl controls/baselines were added to allow cross referencing un-notch (normalize) #s. These samples are not precision prepared, so the testing service will precision machine to exact ASTM dimension. Next test batch, I intent to add 8670 ctrls - improving normalize# relationship between notch & un-notch and different thickness.



btw - I ordered some niolox+ (look like Becut equiv), .2419 (O4? equiv) and 1.2519/O7.
Click to expand...
 
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