Carbidized Edges

T

ToothyEdge

Joined
May 17, 2013
Messages
21
Hi All-

I'm new to bladeforums and originally posted this in the Daniel Fairly Knives hosted forum, but thought it might be more appropriate here.

I recently built a home-brew carbidizer from a Dremel engraver and misc. electronic parts and have been experimenting with it. (Yes, I'm an electronics geek that likes to play with knives.) I was hoping somebody here could help me with a few questions:

1) I've just been using a pure tungsten carbide rod for an electrode, but I've seen "special" ones online that have other stuff (alloys? fluxes?) besides the TC in it to make it work better somehow. What are people using? Is pure TC Ok?

2) The blade seems to stay pretty cool during the TC deposition, but I wonder if it is destroying the temper by heating the blade on a micro scale. Are you guys tempering after carbidizing or before?

3) The first blade I carbidized was chisel ground and I carbidized the flat side. I figured that this would give the best "self sharpening" effect. But, I see other people carbidizing the beveled side on a chisel grind, one side of a double convex or scandi grind, and other combinations. What are the pros and cons of various grinds for carbidized blades? I wonder what happens as the blade wears -- might some of the grinds undercut and weaken the carbidized side as the edge wears?

Thanks. :)
 
Welcome to Bladeforums!



1. I'm not really sure, I use pure Tungsten Carbide. Are you getting some penetration of carbide? you should have a bit


2. I mostly carbidize Titanium so micro-tempering issues are no problem.

I get very little heat buildup, much less than tempering temps as I hold the knife in my bare hands while applying carbide. (would need to measure actual temps of course as we're talking micro tempering)

I have carbidized an O1 steel test knife and am very impressed by the performance especially on cardboard.

Micro tempering may happen but I think it is a non issue as the 72 RC does the cutting.


3. I feel if a bevel is carbidized it should be a zero bevel or on the flat for the best performance. I apply to either the back of a true chisel grind or on the zero bevel main grind... appearance wise it is different but the edge geometry is very close between the two.



I hope this helps! :D Let me know if I can explain anything more... I just ground 12 knives and am worn out, hope everything makes sense! (will be carbidized Ti actually!)
 
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Hi Daniel-

Thanks for the reply. It's great to hear from an expert such as yourself.

I'm new to all of this. I've carbidized some scrap 6AL-4V, but haven't done an actual Ti blade yet. So far the blades I've carbidized have been off-the-shelf knives made from AUS-8 and 8Cr13Mov. I wanted to get some more experience before I try to make my own blade.

I don't know what kind of penetration I'm getting with the TC. How can I tell? It deposits uniformly, cuts nicely, and doesn't scrape off...

I hear you about the 70+ TC hardness rendering the blade tempering moot. I guess I was wondering about the performance of the edge over its lifetime. If the steel lost its temper, maybe the edge would be more likely to fold over with use. I dunno...

My "best" grind question is sort of along the same lines. As the steel wears away, won't the edge geometry get wonky? Why don't you like carbidizing on one side of a secondary bevel?

One more question: What is the best hardness for a blade material with a carbidized edge? Harder should support the TC edge better, but softer might wear faster and expose fresh TC better as it wears. What do you think?

Thanks again.
 
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Thanks for the kind words!

Sounds good on the application penetrating...

I'd have to test and carbidize more steel to really tell on the microtempering. I really just stick to Ti as it lends itself well to the process. I know for fact that the main temper would not change... the knife would need to get to 350F at the least and they get to probably 80-100F.

I feel the wear isn't an issue as the blade would likely be touched up before it wore away very much. I use a shallow hollow grind on the ones that I carbidize on the bevel side so they can be sharpened quite a bit before there is much of an edge geometry change.

Secondary bevel carbidizing - I think that process works fine, it seems that having the carbide edge at less of an angle would be better though. ...They only get sharpened from one side so it makes sense to do a zero bevel in my opinion. I have done some factory double ground knives and they worked very well.

Hardness - Ti works great, on the other hand I have had no edge chipping issues on carbidized hardened steel. I feel this is an area I would like to experiment more in.


I'm going to do some extensive testing and will videotape the process. I carry a carbidized Ti blade often and am very happy with the performance for every day tasks.
 
Thanks again. I'm gonna watch your forum and try to snatch up one of your Ti blades as soon as they're ready. :D

My goal is to make myself "the ultimate" knife for skinning and field boning elk. (I don't want to have to re-sharpen out in the woods.) The problem I've seen with my carbidized chisel grind prototype is that it doesn't cut straight on deep cuts, and doesn't self-center between the hide and membrane, so it ends up nicking the hide when skinning as it curves and bites towards the flat side. If I weren't carbidizing, I think a double convex grind would be my first choice to protect the hide, followed by a symmetrical flat grind with a secondary bevel as a close second choice. Carbidizing complicates the choice, though. ;)
 
+1 on how to make the carbidizer. A step by step WIP with a parts inventory while you're at it.

Welcome to BF btw

Syn
 
ToothyEdge said:
Thanks again. I'm gonna watch your forum and try to snatch up one of your Ti blades as soon as they're ready. :D

My goal is to make myself "the ultimate" knife for skinning and field boning elk. (I don't want to have to re-sharpen out in the woods.) The problem I've seen with my carbidized chisel grind prototype is that it doesn't cut straight on deep cuts, and doesn't self-center between the hide and membrane, so it ends up nicking the hide when skinning as it curves and bites towards the flat side. If I weren't carbidizing, I think a double convex grind would be my first choice to protect the hide, followed by a symmetrical flat grind with a secondary bevel as a close second choice. Carbidizing complicates the choice, though. ;)
Click to expand...

I'd try either grind, just keep the carbidized side a zero bevel.
 
hammon172 said:
Will you tell me how you made your carbidizer. I'm very interested in trying this.
Click to expand...

I'm still "tuning" the voltage, current, and pulse width, so I'm not quite ready to share the design yet. At this point, I've invested more in the project than if I'd just purchased one of the hobby-grade carbidizers you can buy online. :eek:

But, it's been a fun project and in the end, once it's tuned, I hope to get better results than I could get with a hobby carbidizer. :)

k9tfd.jpg
 
Sorry to interrupt such an interesting read with such a basic question, but the experts seem to be here. Why is it that you only carbidize one side of an edge? Why not both?
 
1) It allows you to sharpen the non-carbidized side as the carbide layer is very hard and also very thin.

2) When cutting some materials (like cardboard) it becomes somewhat self-sharpening as the softer metal wears away faster than the carbide, constantly revealing a fresh carbide edge.
 
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I have carbidized some symmetrical double bevel ground blades, carbidizing one side of the bevel only. It works fine. If you want to keep the cutting edge centered on the blade, you will eventually have to grind off the carbidizing and then re-carbidize the reground edge, but that only takes a minute if you have a carbidizer.

The carbidizing process can cause some pitting and general wierdness on a small scale at the cutting edge (not really surprising considering you are beating on the cutting edge with an engraver while micro-welding carbides on to it), a light honing of the un-carbidized side of the blade will usually take care of most of that. But for this reason I have not had good results carbidizing both sides of the cutting edge. A carbidized surface is no longer a perfectly polished flat plane. If you are in pursuit of the ultimate hair whittling edge, carbidizing may not be a good choice for your knife.

Carbidizing can make the edge of the knife hot, it would not surprise me if some tempering of the extreme cutting edge was taking place, but I expect any damaged steel would be worn away quickly and I have not noticed any lasting negative effects. In fact the performance of most of the knives and tools I have carbidized has improved

Remember that while there may be a "self-sharpening" effect when cutting certain materials, your blade is still made of the same material it was before it was carbidized. Hit bone or rock and your blade will chip or roll just like it would before carbidizing.
 
I like Tungsten Carbide (WC) on my steel blades and Titanium Carbide (TiC) on my Titanium blades.
 
Mahoney said:
...Remember that while there may be a "self-sharpening" effect when cutting certain materials, your blade is still made of the same material it was before it was carbidized. Hit bone or rock and your blade will chip or roll just like it would before carbidizing.
Click to expand...

Yah, that's one thing that puzzles me. I've seen reports online of carbidized edges rolling on cheap soft steel blades, but I've not seen any reports of rolling on carbidized titanium blades which are even softer than cheap steel.
 
I suspect the makers of carbidized titanium blades have the edge geometry optimized for the material, and the folks that buy titanium blades are either more careful with their knives, or accept any edge damage as part of the price of using a titanium knife.

Titanium's not all that soft...I don't have a titanium knife, but I do have a titanium hammer, I have pounded many mild steel nails with it, and it is no more dented and dinged than my steel hammers are...
 
IIRC, 6Al4V Ti is somewhere around Rockwell 44C hardness. I guess you don't heat treat it when making a knife.
 
When I had 6al 4v ti hardness tested it was hrc 43 or 44. "heat treating" does absolutely nothing to the hardness of that alloy.
 
Every piece I had tested was mid 30's HRC. Heat treating raised the HRC 1-2 points, which is not worth the effort IMO.

Here are some references regarding 6-4 hardness:
http://www.atimetals.com/Documents/ati_6-4_tds_en.pdf
http://www.efunda.com/materials/all...m.cfm?ID=T18_AB&prop=all&Page_Title=Ti-6Al-4V
http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641

I also spoke to metallurgists at Timet and RMI. We were trying to find the best titanium for knife blades. Both companies recommended Beta C due to it being heat treatable to higher hardness than 6-4.

Beta C does make an OK blade but it is the hardest titanium to grind I've ever found. We've been experimenting with making Beta C san mai blade material. One test sandwiched Beta C between Timascus billets. The next test used zirconium for the outside.

Here is a photo of the zirc/Beta C balisong blade:

Zirc%3ABetaC%20San%20mai%201.JPG

Zirc%3ABetaC%20San%20mai%202.JPG


Chuck
 
It was years back when I had Ti hardness tested, I may be transposing the numbers. I'll see if I can find the piece, I had it in my desk a long time as joke. The only place anyone talks about heat treating Grade 5 titanium for hardness is on internet knife forums. Everyone else in the industry knows it cannot be heat treat for hardness, only for stress relief and to in some cases (like airplanes) to increase the tensile strength. You need a furnace with an argon atmosphere for that.

If you have any heat treating recipe or company who can get ANY increase in hardness out of grade 5 titanoum, I'd love to hear it.

All the bullshit you read on knife forums about people heat treating their lockbars etc is just that: Bullshit.
 
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