W1 TEST/Failure

N

nc_cooter

Joined
Sep 26, 2004
Messages
574
I put my first W1 blade through some test this week end. Cutting test (IE wood ,card board) went well. The edge held up great. Then started cutting some oak and deliberately cut on an off angle. After about a dozen strikes, this is what happened.

W1-test-1.jpg


The arrow in the next pic is pointing to the top of the edge quench line. It's not clear in the pic(crappy camera/photographer) but the change in structure is there.

W1-test-2.jpg


After this, I went on line and asked for some W1 heat treat info. DUH!
Need to temper at 450/475 for two one hour cycles.
Oh well. Try, try again.

PS: Glad I tested it well, someone wanted to purchase.
 
450-475F is quite high, you've got to be able to go lower than that, especially for W1 in that size of blade.
 
ooh thats a PITA, I remember that knife's copper band, maybe you can get elves mend it together for aragorn? just kidding but I feel for your loss.
 
The blade was normalised 3 times and then edge quinched in 130F canola oil. Tempering was 400F for one hour.
 
Joe, my findings are about the same. I would not temper below 450o, and 475o I think is even better.
 
Tempered at 400f, this blade should have been over 60 Rc.

BUT should not have broke, something is wrong here.

Maybe temp too high when normalizing or...

Temp too high when heating to quench or...???

What did you quench in ?
 
Sounds like there was a crack in it. But I would think the soft back would have stopped it...
 
Phillip, you might be right -a quench crack that propagated in use. His photo might show it if it were better.
 
mete said:
Phillip, you might be right -a quench crack that propagated in use. His photo might show it if it were better.
Click to expand...


That's an interesting line of thought, will a quench crack (beginning in the martensite edge) normally propagate up through the pearlite back along grain boundaries in such a straight line? This would seem to indicate a very hard but brittle pearlite structure as well.

The pictures are a bit blurry but it looks like the grain might be a bit coarse.
 
A crack is what I suspected. When hand sanding at 800 gr, thought I could see a slight difference in the finish in the area that broke. I did a heavy etch but could not see anything after another 800gr sanding. That's the reason for the heavy handed testing on the oak.
Will watch the heat on the next blade, temper in the 450/475F range and test the blade to destruction.
Thanks for all the input.
 
Make sure you temper as soon as possible after quenching. Seems like that's especially important with water quenching steels.
 
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