<font face="Verdana, Arial" size="2">Originally posted by Bart student:
People always attach carbon with edgeholding, HRC with edgeholding.....
That's not even close to the truth.
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It is difficult to debate on these forums, in ascii text. I'll let some known references do so for me.
I'll submit that of my references, other than personal experience, here is one that should be a reasonable reference, Wayne Goddard. Here is a guy who has made knives for something very near 30-31 years, stock removal and forging, still does both to this day. If you haven't read his book "Wonder of Knifemaking", then you may not appreciate his direct, honest, open-minded style in pursuit of performance. In any case, I quote from that book on page 152, with another respectable reference, Paul Bos, one familiar to Buck officionados:
"THE EFFECT OF HARDNESS ON EDGE-HOLDING ABILITY -- One of the tests that I did early on, with the help of Paul Bos, was to determine the effect on edgeholding as the hardness changed. Paul is a professional heat-treater and was interested in helping in these tests. We ran test batches of D-5, 154CM, and 440C, giving half the blades their normal working hardness, the other half were drawn back two points on the Rockwell C scale. The blades drawn back two points would cut 15% to 20% less, which surprised both of us. Later when comparing a blade with a hardness of 54 HRC to a blade of 60 HRC, I found the percentage loss held up. The steel that did 40 rope cuts at 60 HRC would do 30 cuts at 58 HRC, 20 cuts at 56 HRC, 10 cuts at 54 HRC, and at a hardness of 52 HRC, would hardly cut the rope one time."
"All test blades are prepared having a width of 1", a thickness of 1/8" and a length of 3-3/4". All blades are flat-ground to 0.20" at edge. Sharpening is done on Norton Fine India Stone, the wire edge (burr) being worked off with the stone. This gives a hair-shaving, long-lasting edge that has what I refer to as micro teeth. Slicing custs are made on a single strand of a 1" rope (a 3-strand 1" rope has 3 fat strands of say 3/8" each). Care is taken to use an equal section of blade from one knife to the other. The edge will bite into the rope strand when freshly sharpened, but as slicing continues there comes a point when the edge no longer is biting into the fibers, and this is when clicing is stopped and the number of cuts is recorded. The edge loses its ability to shave hair at about the same time as it loses its bite into the rope. Each blade is tested at least 3 times and the results are averaged."
I have no interest in debating hardness vs. edge holding here. The only SS type blade materials that come close to even minorly deviating from the above general test results are Stellite/Talonite (Cobalt/Chromium matrix of Rc 42-48, but loaded with Tungsten & Molybdenum carbides, both of which are in Rc 72-77 range) and some of the supersaturated CPM stuff (CPM440V and 420V)... the CPM's slicing longer than they should at softer hardness, and Talonite/Stellite testing soft because of the Rockwell tester's technique of pushing into the soft matrix and not registering the carbides, all the while Talonite/Stellite having tremendous abrasion resistance (related to slicing ability in fibrous/abrasive materials).
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On the subject of corrosion resistance, what typically improves it is free chrome. If the chrome is bound up with carbon as carbides, it does not seem to contribute to corrosion resistance. This is not a very clear relationship to me yet. E.g. CPM420V has 14% chrome but 9% vanadium and beats CPM440V in corrosion tests with 17% chrome and 5.5% vanadium. In this case, it's assumed that the extra vanadium in 420V binds with carbon leaving more chrome free.
However, I will say that after consulting another reference, the Crucible Tool Steel & Specialty Alloy Selector, I will graciously recant my early statement that 440C should beat 420HC in terms of corrosion resistance. According to Crucible, they even give 154CM/ATS-34 somewhat better corrosion resistance marks than 440C. This doesn't align with my own experiences (I have found light rust on my ATS-34 blades occasionally, whereas 440C I have not, but this isn't a controlled test either). I think most people in industry will say 440C has higher corrosion resistance than 154CM, but not Crucible. They also indicate that a "420Prem" that is fairly close to 420HC beats both 440C and 154CM in corrosion resistance. Sorry for the mis-information on this point. 420HC may well very more corrosion resistant than 440C.
I think what you can say is that most of the stainless steels that have more than 13% chrome (D2 runs 11-12% and will rust) are nearly always plenty corrosion resistant for anything most of us normally use blades for. Exceptions would be uncared-for salt-water fish fillet knives or dive knives.
I believe that this Buck forum has probably had an overdose of my input, so I will move on now, hoping I didn't ruffle too many feathers. Ciao.
[This message has been edited by rdangerer (edited 02-19-2001).]
