Broken heat treat? Diagnosis from CRK, help me understand.

Terry M.

Terry M.

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Feb 5, 2006
Messages
2,969
Some of you may remember a few weeks back I was having trouble with the lockbar sticking on my large 21 Damascus and I sought advice here. It was the consensus that I send the knife back in to CRK and see if they could fix the problem and while they were at it, sharpen and "spa treatment" my knife.
Well, I just got the knife back today (boy did I miss it) and it's perfect, of course, but the diagnosis on the order was "broken heat treat" and "we re heat treated it". Since they were already closed when I got home I can't call until tomorrow to find out what this means, but I thought it would be a good thread to start and share here. Can anyone explain this to me? The whole experience was a pleasant one other than having to be without my knife for 4 weeks and I commend Angela and the whole CRK staff for taking care of my problem with such ease and speed.

Now, can anyone help decipher what my problem was? :)
 
Terry M. said:
Some of you may remember a few weeks back I was having trouble with the lockbar sticking on my large 21 Damascus and I sought advice here. It was the consensus that I send the knife back in to CRK and see if they could fix the problem and while they were at it, sharpen and "spa treatment" my knife.
Well, I just got the knife back today (boy did I miss it) and it's perfect, of course, but the diagnosis on the order was "broken heat treat" and "we re heat treated it". Since they were already closed when I got home I can't call until tomorrow to find out what this means, but I thought it would be a good thread to start and share here. Can anyone explain this to me? The whole experience was a pleasant one other than having to be without my knife for 4 weeks and I commend Angela and the whole CRK staff for taking care of my problem with such ease and speed.

Now, can anyone help decipher what my problem was? :)
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They heat-treat the very end of the Ti lockbar to harden it. Maybe that was missed, or needed to be done more. I am not sure how you could break your heat treat, but maybe it's lost in translation. I would guess they re-heat-treated your lock face
 
Thanks Cody. I think that makes sense. I'll probably still call to get the official answer just to ease my curiosity. ;)
 
Terry M. said:
Thanks Cody. I think that makes sense. I'll probably still call to get the official answer just to ease my curiosity. ;)
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Please do and post back here.
I know they carburize or heat treat the TI lock face, but I would love to hear more on it.
Thank you for posting this. I love this stuff.
Matt
 
You bet Matt. No problem. I thought folks might like to read about this. Yeah, I'm a knife knerd. :p
 
Yea, that will be it.

You can't heat treat 6Al4v Ti like you can steel so they're not hardening the material. They heat the lock bar face very hot and very quickly to cause a hard oxide layer to form that helps prevent wear and sticking. As you said it's usually described as "carburising". :)

BellaBlades said:
Please do and post back here.
I know they carburize or heat treat the TI lock face, but I would love to hear more on it.
Thank you for posting this. I love this stuff.
Matt
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Ahaa.
Thank you for that information haze. That is well explained.



Haze said:
Yea, that will be it.

You can't heat treat 6Al4v Ti like you can steel so they're not hardening the material. They heat the lock bar face very hot and very quickly to cause a hard oxide layer to form that helps prevent wear and sticking. As you said it's usually described as "carburising". :)
Click to expand...
 
Haze said:
Yea, that will be it.

You can't heat treat 6Al4v Ti like you can steel so they're not hardening the material. They heat the lock bar face very hot and very quickly to cause a hard oxide layer to form that helps prevent wear and sticking. As you said it's usually described as "carburising". :)
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We will need to get some official feedback on the heat treatment because the description you gave is not quite correct. Carburizing is done in a reducing atmosphere and is in some ways the opposite of oxidizing. You could not form a hard oxide layer by carburizing, you would form a hard carbide layer since carburizing actually refers to the diffusion of carbon into the surface and the reaction with the metal to form carbides.

Titanium can be surface hardened by forming titanium oxide, titanium nitrides, titanium carbides and some other more exotic intermetallics.

My guess is that they probably use oxidation to form titanium oxide because I think that's the least expensive.
 
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There would likely use thermal oxidation since they called it a heat treatment. That would involve heating up the lock face and expose it to oxygen. If the temperature wasn't high enough, oxygen too low or time too short or some other parameter was incorrect they would not get good surface hardening.
 
They heat the lock bar with a flame in air (oxyacetylene torch) to form an oxide layer.... I said it was usually referd to as "carburising" as that is a close enough explanation as to what is done and often the word used to descibe the proces here. Many people don't care about or understand pedantic overly scientific descriptons. :)

rishma said:
There would likely use thermal oxidation since they called it a heat treatment. That would involve heating up the lock face and expose it to oxygen. If the temperature wasn't high enough, oxygen too low or time too short or some other parameter was incorrect they would not get good surface hardening.
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If that is the case how do they get that perfect straight line and shape on the lock bar, that darkened portion is rather perfect looking. Like done by machine somehow? Or do they mask that area off?


Haze said:
They heat the lock bar with a flame in air (oxyacetylene torch) to form an oxide layer.... I said it was usually referd to as "carburising" as that is a close enough explanation as to what is done and often the word used to descibe the proces here. Many people don't care about or understand pedantic overly scientific descriptons. :)
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They do indeed mask it off before sand/bead blasting the part. :)

BellaBlades said:
If that is the case how do they get that perfect straight line and shape on the lock bar, that darkened portion is rather perfect looking. Like done by machine somehow? Or do they mask that area off?
Click to expand...
 
Haze said:
They heat the lock bar with a flame in air (oxyacetylene torch) to form an oxide layer.... I said it was usually referd to as "carburising" as that is a close enough explanation as to what is done and often the word used to descibe the proces here. Many people don't care about or understand pedantic overly scientific descriptons. :)
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I generally agree with this. However, (as a random example) there are quite a few discussions on these forums where armchair metallurgists pontificate about adding 0.01% unobtainum to some alloy in hopes of besting the super steel of the day. I suppose some of them really know what they are talking about, but in the grand scheme, most of us are satisfied knowing that things are done to make things work well, and not exactly HOW these things are done.

...but occasionaly it is fun to know HOW :D
 
Haze said:
They heat the lock bar with a flame in air (oxyacetylene torch) to form an oxide layer.... I said it was usually referd to as "carburising" as that is a close enough explanation as to what is done and often the word used to descibe the proces here. Many people don't care about or understand pedantic overly scientific descriptons. :)
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Sure, you feel better calling it pedantic and overly scientific. Feel free. But calling it carburizing is just wrong. Not "close enough", even if others have called it that. It has a lot of other implications. Your oxyacetylene description makes perfect sense.

You won't typically see me flexing metallurgical might on the forums :). Most of the time it doesn't really matter.
 
I feel no better or worse for it to be honest. IIRC even CRK have referd to it as that as have a large number of people before me. I don't care enough to argue the point or correct it to prove anyone right or wrong. You are correct though. :)

rishma said:
Sure, you feel better calling it pedantic and overly scientific. Feel free. But calling it carburizing is just wrong. Not "close enough", even if others have called it that. It has a lot of other implications. Your oxyacetylene description makes perfect sense.

You won't typically see me flexing metallurgical might on the forums :). Most of the time it doesn't really matter.
Click to expand...
 
Haze said:
I feel no better or worse for it to be honest. IIRC even CRK have referd to it as that as have a large number of people before me. I don't care enough to argue the point or correct it to prove anyone right or wrong. You are correct though. :)
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Wait a minute....if CRK calls it carburizing that could be what they are doing. If the oxy-acetylene has excess acetylene it would be a carburizing flame not oxidizing. Now I am really curious.....though I may be the only one who is.
 
If you have a few moments you can watch the procedure on the CRK shop tour videos. :)

rishma said:
Wait a minute....if CRK calls it carburizing that could be what they are doing. If the oxy-acetylene has excess acetylene it would be a carburizing flame not oxidizing. Now I am really curious.....though I may be the only one who is.
Click to expand...
 
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