Some CATRA test results

Gonna just try to write up an article without the micrographs, no one was willing to get back to me on getting them done. The blades have been sitting too long for them to be relevant anyway. I have done a bit of work with the numbers already, so I can go ahead with that.
 
I worked up about six pages so far, will contact a few involved parties and then maybe send it off to a publication to see if it's fit to print.
 
Have you tried the guys at crucible/latrobe/carpenter in the knife steel sales to try to get them to run this stuff through their labs for you. Promise a good review of their products and they might help.

I'm not sure if Bob at Niagara has the lab setup for this but he's the kind of guy that could get interested in a project like this.

Joe
 
Micrographs were done last month. I have imaging of the edges before and after sharpening and also etched surfaces to show the microstructure. Yes, it has taken this long. Fortunately there were some incredibly accommodating professionals in the steel industry who made it all happen.

I have more grad school work to knock out, then will be getting back into this.
 
Great to see--thanks for staying with this project and for sharing it with us--very generous.

Could you tell us a little about your background and what inspired you to take this on?

Fascinating.
 
Thank you, Hardheart. Wonderful information. I missed it the first time around.

Just to think out loud.

The edge-wear performance was boosted 270 to 378 percent by using a more acute edge angle, compared to gains of roughly 5-10 percent for the heat treat, powder processing of the steel and edge polish. The blade geometry boosted edge-wear performance by roughly 20 percent.

So geometry is the big winner, especially edge geometry, but this is a test only of wear resistance on one medium. I'd guess that both blade and edge geometry could benefit from added strength and toughness, and those qualities might respond much more favorably to heat treat, powder-steel technology.

If you use a knife with good blade geometry, give it as acute an edge as the metal can support and use high-wear alloys at high hardness -- the wear resistance of the edge will benefit greatly. I think Ankerson's results support this reasoning.

So we have some excellent tests of wear resistance, but we don't have matching tests for toughness and strength which would allow us to take blade and edge geometry to the limits of their abilities, given any particular cutting task. And we can't ignore the cutting task. Whittling, for example, might produce much different results than cutting rope or slicing a very specific CATRA medium. And cutting stiff cardboard would, I'd guess, make blade geometry (primary grind) much more important.

But as we mix and match all these variables -- heat treat, steel alloy, blade geometry, edge geometry, powder-steel processing, hardness/strength, toughness, knife tasks -- we end up with an almost infinite possibilities in performance and way, way too many variables to control for in any reasonable experimentation.
 
Yes, edge geometry has the greatest impact, and increased strength will give a greater resistance to plastic deformation for a given cutting force. Since thinner edges cut better, and higher strength allows for thinner edges, higher hardness can mean better edge performance. And PM allows the same alloy content to reach higher hardness with improved impact toughness for the same HT recipe. We do also have tests of the same alloys at different hardness showing that higher hardness/strength improves edge holding.

The tests of strength and toughness are hardness tests and charpy/izod, which are conducted and then edge performance tested. We do find that increasing toughness is not as influential over edge holding for cutting and slicing, though toughness is important for percussive cutting. Cutting stiff and flexible materials have been tested for food prep, harvesting, and wood splitting, and I have copies of those papers. It still holds the same there that higher hardness and thinner edges improve edge life. It does become intuitive when we stop wondering about steel and just thinking about the task. The thinner the wedge, the less force it requires to part the media it is driven through. So starting from that viewpoint, the importance of steel is having the properties that support this task and the geometry required by it, instead of altering geometry to support various steel properties. Because a thinner flat, hollow, or convex grind cut better than thicker versions. A lower edge angle cuts better then a heavier one. I think the major consideration is failure mode and the force required to reach failure.
 
hardheart said:
Yes, edge geometry has the greatest impact, and increased strength will give a greater resistance to plastic deformation for a given cutting force. Since thinner edges cut better, and higher strength allows for thinner edges, higher hardness can mean better edge performance. And PM allows the same alloy content to reach higher hardness with improved impact toughness for the same HT recipe. We do also have tests of the same alloys at different hardness showing that higher hardness/strength improves edge holding.
Click to expand...


That's what some of us have been trying to tell people for awhile now, but some don't seem to listen.... :thumbup:

So at least you have it down on paper from CATRA.
 
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