Finishing CPM3V

B

Blackcatt

Active Member
Howdy,

I have been working with 3V a little recently and I really like this steel. Not bad on the belts and finishes up nicely.

My question is on corrosion prevention. What are my options as far as bluing etc? What have you used with success? Methods or specific products would be most appreciated.

Thanks
 
I etch my 3V blades in a diluted solution of ferric chloride and deionized water. I think that helps get rid of some of the surface carbon. After it has etched, I clean off the carbon and go over the surface with an OOO scotch brite pad. The blade will have a gray look to it. Overall, 3V has better corosion resistance than carbon steel. It can pit if it stays in a moist environment without any oil or wax on the blade. Renaissance wax is a great protector.
-John
 
I'm grinding my first batch of 3V blades and I'll be watching for more tips. I've read almost everyone etches them like John described.

What I've heard so far is to grind as clean as you can before HT cuz it's so tough to grind after. I'm taking these right up to 600-grit... will let you know how post-HT goes.
 
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James Terrio said:
I'm grinding my first batch of 3V blades and I'll be watching for more tips. I've read almost everyone etches them like John described.

What I've heard so far is to grind as clean as you can before HT cuz it's so tough to grind after. I'm taking these right up to 600-grit... will let you know how post-HT goes.
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You're going to miss out on the experience of hand-rubbing 3v with 400 grit... makes it feel like 1200. What's wierd is switching to an A2 blade and feeling the paper cut, after 3v slides off it like rubbin' glass on glass.
 
It's not that bad. I take it to 100 microns before HT. Then after HT take the flats to 45 microns and the grind down to 16 microns. Start rubbing using Mobil one. I only take 3V to a 400 grit hand rubbed finish. No use to go any higher. It's definitely easier than S30V. 3V is the best knife steel for performance IMO, CTS-XHP is my next favorite for 3 reasons. It is easy to HT and doesn't need to be sent out. It grinds like a dream and is easy to hand rub. It holds an edge forever, but is easy to sharpen. 3V performs better, but has to be professionaly HT'ed, is tough to grind and finish, and is hard for the average guy to resharpen at home. Good luck guys.
-John
 
I learned about Mobil 1 from Frank here on the forum, I like it. So far my favorites are O1 and CPM-154, but I heard so much about 3V I had to try it for all the reasons you mention. I'm going to have Brad from Peter's HT deal with that part. Thanks to Murph's GAW I'll get to try a piece of CTS-XHP soon, it sure sounds good from what everyone says :thumbup:
 
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i love 3v and since i have an even heat and cryo here at the shop i dont send mine out :)

so far as a finish
i use gator belts to A45 cork or scotbrite belt and call it a day for workers and have tested my necker with that finish in hot tubs showers and the beach

after i got off the beach i showered off at the shower house thing jsut to get the salt off and never dryed it in the kydex sheath
no problems with pitting or rust i have found tho if i etch he blade that it wil get rust much faster and the best hand rubb finish from a rust standpoint is 400-600 range and a light buff to soften the tops of the scratch pattern

im not goingto tell you that 3v is dam near SS but its sure a pile better then any of the std tool steels (O1 A2 and the like )
and so far in my testing cpmM4 will rust a bit faster but not bad (i was worried that my dress knife might get ugly fast )
 
I found this over on BFC:

Jerry Hossum said:
The problem with corrosion on 3V is the presence of oxides in the steel at the surface. It's a product of the production process and is what makes the steel susceptible to the rust spots/pitting that can happen. By etching the steel, I remove those oxides and even though the patina in many circumstances might increase susceptibility to corrorion, it doesn't in this case, possibly because I brush the steel back to a fine finish after etching...

While 3V is certainly not stainless, it does contain enough free chromium to provide some anti-corrosion protection. When I first used the steel and noted how it corroded, widely scattered spots of orange rust under which were fairly deep pits, I ask the then chief metallurgist at Crucible Steel about what I saw. He said the spots were the result of surface oxides, presummably iron oxides. I'm guessing these oxides are contaminents in the CPM powders which are then trapped in the steel when it is hipped. With that in mind, I reasoned that I could remove those particular oxides with an acid bath. Whether the reasoning is correct or not, it worked and I've seen a much reduced tendancy for 3V to corrode after "passivation". Whether it is the formation of Chromium oxides from the free chrome or simply removal of the problematic iron oxides, I really don't know.

I now "passivate" all the steels I use, CPM-3V, CPM-154 and S30V. I like the patina that's formed and whatever else it does is like chicken soup, can't hurt.
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Here is a pdf explaining passivation. It's a bit wordy, but here's the gist of it:
In layman's terms, the passivation process removes “free iron” contamination left behind on the surface of the stainless steel as a result of machining and fabricating processes.
These contaminants are potential corrosion sites which, if not removed, result in premature corrosion and ultimately result in deterioration of the component. In addition, the passivation process facilitates the formation of a very thin, transparent oxide film, which protects the stainless steel from “selective” oxidation (corrosion). So what is passivation? Is it cleaning? Is it a protective coating? In my opinion, it is a combination of both!
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Butch,
I have an evenheat oven, aluminum quench plates and cryo, but I still have not been successful getting it quench fast enough to get a Rockwell over 57. That's why I send it out. I want it to be about 61. What hardness are you getting doing it yourself?

James,
Great post. That's what I've read before too.

-John
 
John Barker said:
Butch,
I have an evenheat oven, aluminum quench plates and cryo, but I still have not been successful getting it quench fast enough to get a Rockwell over 57. That's why I send it out. I want it to be about 61. What hardness are you getting doing it yourself?

James,
Great post. That's what I've read before too.

-John
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I do not have a hardness tester but have compared my 3v with commercially HT'd samples in cutting tests and have found no deficiency in the hardness I am getting. I quench with cold (frozen) plates, with the blades removed from the foil, and use forced air between the plates at about 60 psi. I can take them out of the plates and handle them within a minute of them leaving the oven at 1950.
I am going to send a run out to Peter's for HT and do some more comparison testing but the HT I have now produces a blade that will easily out-cut A2 at 59-60.
 
Justin, send 'em an already HT'd blade too and have them RC test it for you.

I bet they'd do it, and you'll see what your getting at home.
 
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