Blade testing results summary and lessons learnt

aarongough

aarongough

Joined
Mar 12, 2013
Messages
1,167
First up I just want to say thank-you to everyone on BladeForums for being so welcoming and for giving me advice and encouragement as I worked my way through my steel/blade testing!

The testing thread has gotten pretty long, so I wanted to summarize the results and the lessons I learnt so that they're a bit more pleasant to read. Hopefully they'll be of value to someone else.

Just to emphasize again, these results are probably pretty specific to my heat-treatment and my blade geometry at the very least. I think they're interesting, but I'm not in any way trying to say that they're the last word on the steels involved.

These results are mainly based around impact resistance because differentiating the blades by edge-retention is extremely difficult and time consuming. I'm also focusing on hard-use knives right now so impact resistance (and abuse resistance) is a primary concern. All the steels held an edge very well from what I could see (except 440C with a bad heat-treat).

Best:
Blade 10 - CPM3V Ver2 (60.5HRC)
Blade 2 - A2 Ver1 (59.5 HRC)
Blade 5 - CPM3V Ver1 (61.1 HRC)
Blade 8 - O1 Ver2 (59.7HRC)
Blade 7 - CPM154 Ver2 (62HRC)
Blade 1 - CPM154 Ver1 (59.6 HRC)
Blade 11 - A2 Ver2 (60.5HRC)
Blade 12 - 440C Ver2 (59.5HRC)
Blade 3 - O1 forge (55-60HRC)
Blade 4 - O1 Ver1 (60.6 HRC)
Blade 6 - 440C Ver1 (59.1 HRC)
Blade 9 - A2 Ver2 (62.5HRC)
Worst:

Overall I'm happy with the outcome. I would happily make hard-use blades from any of the top 4 steels, I'm leaning toward A2 though as it's more corrosion resistant than O1, and is easier to get in a wider variety of sizes that CPM3V. It's also less expensive and easier to heat-treat, and offers very similar performance except when it's pushed to the absolute limits. CPM154 seems like it would be a good candidate too provided that my designs are adjusted to provide some extra tip strength.

Lessons learnt about heat-treatment:
1) With adequate heat-treat it seems that all the blade steels steels tested offer great edge-retention.
2) When the heat-treat is not ideal (as with 440C Ver1 in the first test) all of the properties of the blade suffer greatly.
3) Seemingly insignificant changes in the heat-treatment process can yield huge improvements in the result. Or they can be hugely detrimental.
4) Blades need to be taken to a fine finish before H/T when using anti-scale compounds.
5) If quench speeds are changed, or cryo or sub-zero treatments are introduced, tempering temperatures will need a bunch of tweaking!
6) Harder blade steel does not necessarily equal better edge retention, even in the same steel! Each steel has a sweet spot for each application.

I know that points #1 and #2 are well known and often stated, it was just interesting for me to see first-hand the huge difference that it can make. Comparing O1 Ver1 and O1 Ver2 in the list above will highlight this. Point #6 was something I was already aware of, but again it was very interesting to see the results up close.

Lessons learnt about testing:
1) Testing steels comparatively for edge retention is HARD. Really, really, hard. Lots and lots of time can be (and was) eaten by this, and my results really weren't even very useful.
2) Testing toughness/impact resistance in an informal way is relatively easy and I think it has a lot of value.
3) Testing different heat-treats is really valuable and I'll likely keep tweaking and testing. (I'm sure most makers do too)

Lsssons learnt about assuring quality:
1) A rockwell tester really is an invaluable tool. It's a shame they don't make a small version specifically for knifemakers.
2) Decarburization seems to show up as lighter colored patches after etching a blade with Ferric Chloride for a few seconds.

Some snappy fun facts about what went into the testing:
  • 5 grinder belts of various grits
  • 9 feet of various tool steels
  • The kiln was on for approximately 70 hours doing heat-treatments
  • 84Gb of digital video footage was taken during the testing (2 hours or so of footage)
  • More than 120 sharpening sessions
  • Over 150 feet of 1/4" sisal rope
  • Over 36,160" linear inches of cardboard cut (3,013 feet, or just one kilometer!)
  • The testing in total took more than 178 hours over 5 weeks.

If you've gotten this far and you're still not sure what I'm talking about, check out the original thread here: http://www.bladeforums.com/forums/showthread.php/1104795-Steel-testing-underway

If anyone has critiques or suggestions for heat-treatments or test methods I'd love to hear them!

Thanks for reading along, I've very much enjoyed getting to share the process with you all!
-Aaron

---------

Here's a summary of all the heat-treatments I used in the testing:

Round 1:

CPM3V Ver1 (blade #5):
Preheat to 1500ºF, Equalize
Ramp to 2050ºF, hold for 20 minutes
Quench in air to below 125ºF
Temper at 1000ºF, 3 times, 2 hours each -> 61.1HRC

440C Ver1 (blade #6):
Preheat to 1425ºF, equalize
Ramp to 1900ºF, hold for 20 minutes
Quench in air to room temperature
Temper at 300ºF, 2 times, 2 hours each -> 59.1HRC

CPM154 Ver1 (blade #1):
Preheat to 1400ºF, equalize
Ramp to 1900ºF, hold for 60 minutes
Quench in oil to below 125ºF
Cryo-quench into dry-ice & isopropanol for 20 minutes
Temper at 400ºF, 2 times, 2 hours each -> 59.6HRC

O1 Ver1 (blade #4):
Preheat to 1250ºF, equalize
Ramp to 1500ºF, hold for 15 minutes
Quench in oil to 150ºF
Temper at 400ºF, 2 hours
Cryo-quench into dry-ice & isopropanol for 20 minutes
Temper at 400ºF, 2 hours -> 60.6HRC

A2 Ver1 (blade #2):
Preheat to 1100ºF, equalize
Ramp to 1775ºF, hold for 35 minutes
Quench in air to below 150ºF
Temper at 400ºF, 2 hours
Cryo-quench into dry-ice & isopropanol for 20 minutes
Temper at 400ºF, 2 hours -> 59.5HRC

O1 Forge (blade #3):
Heat in forge until dull cherry-red color
Quench in oil immediately
Temper at 400ºF, 2 hours, twice -> 55-60HRC

Round 2:

A2 Ver2 (blade #9 & #11):
Double coat in anti-scale (ATP-641)
Stress relieve: Ramp to 1200ºF, hold 2 hours, furnace cool to 900ºF, cool in still air to room temperature
Ramp to 1740ºF @ 400ºF/hr, hold 20 minutes
Oil quench until no longer glowing, then cool in still air to room temperature
Sub-zero treatment in dry ice and isopropanol for 45 minutes
1 blade: Temper @ 4250ºF, twice, 2hrs each time -> 62.5HRC
1 blade: Temper @ 600ºF, twice, 2hrs each time -> 60.5HRC

CPM154 Ver2 (blade #7):
Wrap in stainless foil envelope
Stress relieve: Ramp to 1200ºF, hold 2 hours, furnace cool to 900ºF, cool in still air to room temperature
Preheat to 1400ºF, hold 10 minutes
Ramp to 1900ºF, hold 60 minutes
Plate quench to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 400ºF, twice, 2hrs each time -> 62HRC

O1 Ver2 (blade #8 ):
Double coat in anti-scale (ATP-641)
Stress relieve: Ramp to 1200ºF, hold 2 hours, furnace cool to 900ºF, cool in still air to room temperature
Preheat to 1200ºF, hold 10 minutes
Ramp to 1470ºF, hold 30 minutes
Quench into oil to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 400ºF, twice, 2hrs each time -> 59.7HRC

CPM3V Ver2 (blade #10):
Enclose in stainless foil envelope
Stress relieve: Ramp to 1200ºF, hold 2 hours, furnace cool to 900ºF, cool in still air to room temperature
Preheat to 1500ºF, hold 10 minutes
Ramp to 1975ºF, hold 30 minutes
Plate quench to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 975ºF, three times, 2 hrs each time -> 60.5HRC

440C Ver2 (blade #12):
Enclose in stainless foil envelope
Stress relieve: Ramp to 1200ºF, hold 2 hours, furnace cool to 900ºF, cool in still air to room temperature
Preheat to 1500ºF, hold 10 minutes
Ramp to 1875ºF, hold 30 minutes
Plate quench to ambient
Sub-zero treatment in dry ice and isopropanol for 45 minutes
Temper @ 400ºF, 2 times, 2 hrs each time -> 59.5HRC
 
I certainly am missing something with this testing you did. Was this to tell me that I should pick the steel to use from what you have done here? Was it to tell me I should test all the steels I want to use, or that I should figure the process to do the hardening and disregard the recommended factory steps. If you are saying that good knife making steels heat treated correctly with proper blade geometry will and can provide good cutting edges, I do believe that is true. Seems like a lot of effort as you yourself said to provide information that's been out there for years but some just don't want to read or make a change for. How about trying out some Elmax or M390? Frank
 
thanks aaron for such a hard work to provide us data and lesson. I can assure you that time & sweat you put into this project are deeply appreciated by many of us & this knife community! Thank you.
 
I really enjoyed this thread, and would check back often to see what new results were posted. Thanks for all the effort in doing this.
 
Frank Niro said:
I certainly am missing something with this testing you did. Was this to tell me that I should pick the steel to use from what you have done here? Was it to tell me I should test all the steels I want to use, or that I should figure the process to do the hardening and disregard the recommended factory steps. If you are saying that good knife making steels heat treated correctly with proper blade geometry will and can provide good cutting edges, I do believe that is true. Seems like a lot of effort as you yourself said to provide information that's been out there for years but some just don't want to read or make a change for. How about trying out some Elmax or M390? Frank
Click to expand...

Honestly I'm not really trying to tell anyone else anything with the testing I did. I hope neither of the threads have come across as preachy as that's not the goal. The testing was mainly done so that I could find the steel(s) that I'm comfortable with, as well as suitable heat-treatments. I like to share the journey when doing things like this so that more experience people can help out (and catch the mistakes), and so that other less experienced people can learn along with me.

From what I've seen testing any steel you're going to use along with a couple of heat-treatments seems like a good idea. None of the heat-treats I did were really that different from factory recommendations, they generally recommend a range of austenitizing temperatures, hold times, and temper times. I just tried a few different combinations. The benefits (and detriments) of this were tangible in several cases.

As you said 'good knife making steels heat treated correctly with proper blade geometry will and can provide good cutting edges', however the definition of 'good steel' and 'heat treated correctly' is very dependent on the design and the intended use of the blade... That was the main thing that I needed to test, and the reason why the testing was done.

For me personally at least I think that my choosing from the common blade steels based solely on the impact resistance is probably not a bad way to go for my hard use knives. Whether that's an approach that works for others is up to them, and this policy will only work for me while I'm doing hard-use knives, once I start making kitchen knives the priorities will change again.

I would love to try some other blade steels! Sleipner, ELMAX, M390, Vanadis 4 Extra, CPMM4, AEBL-L, 1084, 52100, and many more! However I'm going to hold off for a while until I believe that I can do the testing justice.
 
kodachi said:
thanks aaron for such a hard work to provide us data and lesson. I can assure you that time & sweat you put into this project are deeply appreciated by many of us & this knife community! Thank you.
Click to expand...

No worries mate, I hope it was of some use!
 
machinistbutler said:
I really enjoyed this thread, and would check back often to see what new results were posted. Thanks for all the effort in doing this.
Click to expand...

No problem mate! I really had to do it all in order to make sure I was happy with my knives going forward, if it helps you guys as well then that's a great added benefit!
 
Very cool! It's really nice how you consolidated all the important stuff, as well as the "fun facts" (which were in fact fun!) into this new short thread. I know I enjoyed reading your thread and looked for new posts often as well, it was very interesting and fun to see "what would happen nex"' lol.

I'm confused how some people aren't understanding your reason for all this testing when it's clearly stated above, as well as plenty of times in the original thread. Anyway, it's incredible how organized and final and precise and thorough you are with all of your testing as well as documenting. Keeping track of how many inches total of cardboard you cut, lol that would be a big task in and of itself. So I just thought I'd tell ya that I appreciated all the work and effort you put into this. Even if some of the infomation you posted can be found elsewhere, it certainly wasn't done in vain, because like I mentioned you're so precise and thorough in your ways and that alone can be very valuable to others while reading, and at the least if it's not useful, it can still be entertaining :)
Great work brother, and I can't wait ta see some vids/ threads on your future knives that will be made with this new found info! Take care :)

-Paul
______________
(some of my work) www.youtube.com/Lsubslimed
 
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So perhaps my remark should have been did you find that the manufacture's offered information was reasonably accurate and the information they provide is sufficient to go with or it's necessary to go through testings similar to what you did in order to get a true picture of what is real? I found long ago in my life that for me the "doing" is the thing. The testing takes away from that. I don't use a lot of different steels since I make knives for certain uses only. If I have information from the steel maker is there a reason to not trust the results that should be ?
Several years back I used ATS-34 for the many hunting knives I made I would have the blades professionally heat treated with the liquid nitrogen treatment included. I have a few years back picked out other stainless steels that are known to give better results just by the information supplied by the manufacturer of the steel.So do I understand right that for you , it is necessary to take these steels and test them out before placing that type of steel into use by you? I unfortunately don't find you have shown me any startling information on the steels you tested. What are you showing here? It's not a cutting comparison. It's great if this has provided some "steel" education to some makers. Increasing knowledge is a great thing but when already provided the testing and retesting seems to me to be very redundant. Sure for many of us the repetition is the best way to learn and seeing information presented in a different manner can certainly help. Frank
 
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Frank Niro said:
So perhaps my remark should have been did you find that the manufacture's offered information was reasonably accurate and the information they provide is sufficient to go with or it's necessary to go through testings similar to what you did in order to get a true picture of what is real? I found long ago in my life that for me the "doing" is the thing. The testing takes away from that. I don't use a lot of different steels since I make knives for certain uses only. If I have information from the steel maker is there a reason to not trust the results that should be ?
Several years back I used ATS-34 for the many hunting knives I made I would have the blades professionally heat treated with the liquid nitrogen treatment included. I have a few years back picked out other stainless steels that are known to give better results just by the information supplied by the manufacturer of the steel.So do I understand right that for you , it is necessary to take these steels and test them out before placing that type of steel into use by you? I unfortunately don't find you have shown me any startling information on the steels you tested. What are you showing here? It's not a cutting comparison. It's great if this has provided some "steel" education to some makers. Increasing knowledge is a great thing but when already provided the testing and retesting seems to me to be very redundant. Sure for many of us the repetition is the best way to learn and seeing information presented in a different manner can certainly help. Frank
Click to expand...

Hi Frank,
Personally I learnt many things from the testing. Some of them may be 'obvious' to a more experience maker, but learning those 'obvious' things can take years of exposure to knifemaking and different steels. I didn't have years available so I needed to condense everything into a shorter chunk of time which is what the testing was all about.

One point that I feel important to emphasize is that no steel manufacturers say "Austenitize at X, Quench in X, Temper at X". They always say "Austenitize at 1950-2050ºF, Air or positive pressure quench or salt or interrupted oil, Temper between 1000-1050ºF". (That's straight from Crucible's datasheet for CPM3V by the way). Results will vary hugely between different combinations of those factors as we saw in the testing, and I can't imagine any reasonable way to predict performance without testing.

It's also worth noting that sometimes the manufacturers datasheet does not give you the best info for knife applications. For instance the crucible datasheet for 440C does not mention anything about cryo or sub-zero treatments for 440C. We saw in the testing though that adding in a sub-zero treatment for 440C significantly improved it's toughness and edge holding. This is also something that would be impossible to predict without testing.

On the other hand, if you are able to get information from other knifemakers about the way they treat a certain steel, I think it's probable that you can treat that information as good. They likely did some testing to arrive at the point where they were happy though.

Finally: blade geometry plays a huge part in how tough a blade is. Testing this is especially important to me as half my upcoming customers are actively serving in the military or in a police organization. They're not going to go easy on their knives. Most of the other half of my customers are serious outdoorsman, they're not going to go easy on their knives either.

I can't make a knife from a new (to me) steel, do the heat-treat on it, then look at it and say "that should be adequately tough". I can say 'that will probably cut things well', different blade geometries and steels are probably going to fine skinning a deer (there are different shades of 'fine' obviously), they may not all deal so well with being batoned through a chunk of hard firewood though.

In short, for me testing is vital. I'm not trying to say that I think everyone needs to spend a month testing. For most people taking one blade and testing it hard will probably do the trick. For me, given that my knives are intended for hard-use, testing is the only thing that lets me sleep at night!

-Aaron
 
coldsteelburns said:
Very cool! It's really nice how you consolidated all the important stuff, as well as the "fun facts" (which were in fact fun!) into this new short thread. I know I enjoyed reading your thread and looked for new posts often as well, it was very interesting and fun to see "what would happen nex"' lol.

I'm confused how some people aren't understanding your reason for all this testing when it's clearly stated above, as well as plenty of times in the original thread. Anyway, it's incredible how organized and final and precise and thorough you are with all of your testing as well as documenting. Keeping track of how many inches total of cardboard you cut, lol that would be a big task in and of itself. So I just thought I'd tell ya that I appreciated all the work and effort you put into this. Even if some of the infomation you posted can be found elsewhere, it certainly wasn't done in vain, because like I mentioned you're so precise and thorough in your ways and that alone can be very valuable to others while reading, and at the least if it's not useful, it can still be entertaining :)
Great work brother, and I can't wait ta see some vids/ threads on your future knives that will be made with this new found info! Take care :)

-Paul
______________
(some of my work) www.youtube.com/Lsubslimed
Click to expand...

Thanks mate! Glad you enjoyed the thread!

Honestly I'm quite please that it's all gone over as well as it has. This kind of testing has the potential to start a massive flame war as people are invested in their particular steels. As you saw, to alleviate this I tried to make it clear that my results are only applicable to my circumstances.

Healthy skepticism is always something that's appreciated on my part, as it makes me look harder at the process and the results and find things that I may have missed otherwise!

I personally wish there was more of this kind of testing out there for us to read. For instance I'd love to see a thread where someone takes 1 type of steel and does like 6 or more different heat-treats on it. That's the kind of thing that I find fascinating and informative! That also may well be something that I look at doing in the future, if I can come up with some better testing methods.

-Aaron
 
Thanks for the replies Aaron. This knife making certainly is area where many different approaches are used to get results. I do believe "it's not what you use or how you get there, but how good the results are." Frank
 
I just found this thread tonight - very interesting info here. You've sure done a LOT of hard work, not to mention the expense of all the metal used.... and fun test equip you've got. Those Rockwell testers sure are NICE.

Keep up the good work,

Ken H>
 
Well, Aaron, mate, someone already has done some testing and has the information that we all like on Elmax. You won't have to go through it all if you read it. Frank
 
This morning I saw the youtube film you made about the testing. Verry interesting to see and how thorough your testing was.
I'm glad I have a CPM 3V knife :-)
 
Ken H> said:
I just found this thread tonight - very interesting info here. You've sure done a LOT of hard work, not to mention the expense of all the metal used.... and fun test equip you've got. Those Rockwell testers sure are NICE.

Keep up the good work,

Ken H>
Click to expand...

Thanks Ken! Glad you found it interesting!
 
Ruudr said:
This morning I saw the youtube film you made about the testing. Verry interesting to see and how thorough your testing was.
I'm glad I have a CPM 3V knife :-)
Click to expand...

I was very pleased I was able to get the video finished yesterday. It's taken quite a while to edit it! That's the first video I've done with my new camera, and I also got a better microphone to do the voiceover, very happy with the results overall!

CPM3V is a great steel!
 
Frank Niro said:
Well, Aaron, mate, someone already has done some testing and has the information that we all like on Elmax. You won't have to go through it all if you read it. Frank
Click to expand...

Sounds awesome! Do you have a link to the testing you're referring to?

-Aaron
 
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