Expected Performance of 1084 HT to ~58-60 HRC?

[J. Keeton]

So I recently did some testing on a blade that I "botched" the heat treat on. This was before I build my new, easy to control, forced air burner...

I estimate that I quenched this blade @ around 1,700+ F. The over heating of the blade is apparent with this blistering pattern.

(Yall taught me this in this thread https://www.bladeforums.com/threads/is-this-what-decarb-looks-like.1615017/)




Since I know that this blades HT was botched, I decided to use it as a test knife. I tempered it with two - 2 hour cycles @ 410F. After tempering I ground though "blistered" surface finish. I then attached micarta handle scales with G-Flex epoxy and 2 brass corby fasteners.

I also wanted to see how hard it was to get the scales to part from the handle.




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So to my fun theoretical question (that I'll have to empirically test with a non-botched knife)... Do yall think the performance of this knife was on par or worse than if I hadn't botched the HT temperature?

To re-phrase: How do you think a 1084 blade quenched at 1,500 F would have compared to this blistered blade?

Bonus: How much would you expect a knife like this to flex in degrees before breaking if the HT was on point and the hardness was targeted @ around 58-60 HRC?

It was fun to break this guy... I'm just wondering some of these things out loud here.

Cheers!





Actual testing starts around 1:50

Edit:

 

[jdm61]

Accodting to Kevin Cahsne's website, the "standard" recipe of 1500/400F will give you 60-61 Rc with 1084 assuming best methods. That will work quite well for most applications. He specifically says not to go any higher than 1500. I have never gone any higher or lower.

 

[J. Keeton]

Accodting to Kevin Cahsne's website, the "standard" recipe of 1500/400F will give you 60-61 Rc with 1084 assuming best methods. That will work quite well for most applications. He specifically says not to go any higher than 1500. I have never gone any higher or lower.

10-4, so in this situation I definitely went higher. I'm guessing if I hit the 1500/400F mark I would have gotten more degrees in my flex test.

I'm certain that I've "engineered" out the possibility of this happening to me again, but it's interesting to see how a blade quenched at a higher than optimal temperature performs.

 

[Larrin]

Wow that really snapped bad.

 

[Stacy E. Apelt - Bladesmith]

I think he broke it intentionally to see the grain.

J.Keeton
Flex is a product of geometry and thickness, not hardness. Hardness determines whether is takes a permanent bend or breaks. I feel flex is a poor indicator of much beyond looking cool in tests on FIF, and in the non-real world tests of the ABS.

A little flex, say 10-15 degrees is probable with a 1/8" hunter, while 45-90 degrees is normal on a .060" fillet blade.
I have an antique sword blade from Scotland that I regularly bend in a 90 degree arc as a demonstration of what a good HT and proper geometry can do.

I found a photo from Ashokan with me starting to bend it:

 

[J. Keeton]

I think he broke it intentionally to see the grain.

J.Keeton
Flex is a product of geometry and thickness, not hardness. Hardness determines whether is takes a permanent bend or breaks. I feel flex is a poor indicator of much beyond looking cool in tests on FIF, and in the non-real world tests of the ABS.

A little flex, say 10-15 degrees is probable with a 1/8" hunter, while 45-90 degrees is normal on a .060" fillet blade.
I have an antique sword blade from Scotland that I regularly bend in a 90 degree arc as a demonstration of what a good HT and proper geometry can do.

I found a photo from Ashokan with me starting to bend it:

It was intentional!

That picture is awesome! You look so happy!

Very good points about geometry and thickness. I'm going to have to perform this same test with the exact same geometry and spot on HT... That's the only way I'll know for sure how badly the blistered blade really performed.

 

[Natlek]

So , in the name of science you destroy perfectly good knife

 

[DanF]

So , in the name of science you destroy perfectly good knife

Happens a lot!

 

[Stacy E. Apelt - Bladesmith]

So , in the name of science you destroy perfectly good knife

No, it was an overheated blade that had surface damage.

And, yes, people will break blades to check their HT. I don't know a good maker who hasn't done that.

 

[J. Keeton]

... and it was fun

I'm sure it won't be the last time!

One of the major components I was "testing" in my eyes was the handle construction as well. It did a pretty good job @ holding together. You can see it start to part from the knife during the second flex test.

 

[Willie71]

Accodting to Kevin Cahsne's website, the "standard" recipe of 1500/400F will give you 60-61 Rc with 1084 assuming best methods. That will work quite well for most applications. He specifically says not to go any higher than 1500. I have never gone any higher or lower.

I did the charpy tests at 1475f. Some of Aldo’s 1084 has been up to 0.87% carbon, putting it into the hypereuctoid range, even if just by a bit. 1080 probably does better at 1500-1525f. I should do a series of samples to tease out optimum aust temp.

 

[J. Keeton]

I did the charpy tests at 1475f. Some of Aldo’s 1084 has been up to 0.87% carbon, putting it into the hypereuctoid range, even if just by a bit. 1080 probably does better at 1500-1525f. I should do a series of samples to tease out optimum aust temp.

So if it's in the hypereuctoid range, does that mean it is better to quench at 1475? I apologize for my ignorance.

 

[Willie71]

So if it's in the hypereuctoid range, does that mean it is better to quench at 1475? I apologize for my ignorance.

Not 100% sure. We quench 1095, O1, and spicy white at 1475f. We quench W2 at 1460f. I have to do some testing to see if there is any benefit to 1475f compared to 1500f. If you have excess carbon, lowering aust temp reduces the carbon in solution to the euctoid point, preventing retained austenite. I used 1475f as an educated guess.

 

[Stacy E. Apelt - Bladesmith]

As a general rule in carbon steels, the higher the carbon, the lower the austenitization target. The eutectoid steels are around 1500-1525F hyper-eutectoid is 1450-1475F, hypo-eutectiod is 1525-1550F.

 

[Willie71]

As a general rule in carbon steels, the higher the carbon, the lower the austenitization target. The eutectoid steels are around 1500-1525F hyper-eutectoid is 1450-1475F, hypo-eutectiod is 1525-1550F.

To add to what you are saying, other alloying elements shift the aust temp too. Nickel lowers it, which is why I do 15n20 at 1460-1470f, but chromium raises the aust temp, which is why 52100 likes 1500-1525f, and stainless steels are in the 1800-2000f range.