I Tested the Edge Retention of 48 Steels

Interesting. It seems sharp in the video but not unusually so. Is it cast or ground?
 
me2 said:
Interesting. It seems sharp in the video but not unusually so. Is it cast or ground?
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We need to sharpen it properly so that it will be really sharp. That is why we want to verify edge retention, although by theroy it has good edge retention. It also resists sea water, acid and base. Check test in 20% HCL.
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How about ductility and toughness? Classically these are fairly low in amorphous materials.
 
me2 said:
How about ductility and toughness? Classically these are fairly low in amorphous materials.
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Property​
Metric ​
English​
Yield Strength​
1600 MPa​
232, 060 psi​
Tensile Strength​
1850 MPa​
268 ksi​
Young’s Modulus​
96 GPa​
13, 923 ksi​
Shear Modulus​
34.3​
4, 975 ksi​
Flexural Strength ​
2000 MPa​
290 ksi​
Flexural Modulus​
65 GPa​
9, 428 ksi​
Poisson’s Ratio​
0.36​
0.36​
Charpy Impact​
6.5 J/cm2​
31 ft lb/in2​
Fracture Toughness​
28 MPa. m1/2​
25, 481 psi.in1/2​
Fatigue Strength ​
300 MPa​
43.5 ksi​
Impact Strength ​
800J/m​
15 ft-lb/in​
Elasticity ​
1.8 %​
1.8%​
 
This is quite the experimental anecdote. Ive found over the years different steels respond differently when sharpening methods vary. And of course small samples of one particular steel will often very from other small samples of the same steel. Particularly when going between different blade smiths who heat treat differently. My years of lapping stones and hones has taught me the difference between when I started sharpening, and where I have ended up now decades later is learning to understand what the steel is doing, and being able to feel that through the stone and adjusting to the steel's reaction for the best long lasting edge. Thats the difference between just knowledge and skill to accompany it. Just recently I was sent a rather nice blade from a very desperate knife owner who was upset that the money he spent on the blade did not match it's edge dulling after cutting cardboard boxes. After I worked out the large scratches from the coarse diamond plate he owned, I was able to work it up a progression of 4 stones that involved more than one angle. When I was done the blade managed to carge knotty pine for 3 hours, cut through a turkey bone, and still passed the hanging hair test. The owner was quite amazed when I showed him documentation of this result.
 
Larrin said:
Recently I was able to acquire a used CATRA machine, so I heat treated just about every knife steel I had, made 57 knives with the help of knifemaker Shawn Houston, and tested them all to see which cut the longest. For a few of the steels I did multiple heat treatments to look at a couple variables and to see the effect of hardness. I also compared edge retention and toughness to see which steels have the best balance of properties. https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
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Why not test ease of sharpening and what steel got sharpest?
 
CATRA test result, 53.5 for sharpness and 132.4 for edge retention for our newly developed 6 inch amorphous metal blade
 
Just a guess, but I would assume that the steels with a very fine grain and low carbides would be the easiest to sharpen.
 
SharpBits said:
Just a guess, but I would assume that the steels with a very fine grain and low carbides would be the easiest to sharpen.
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You would think but honestly they all got very sharp very easily, It just goes to show what happens when you have everything at the same geometry, using the same angle and the same abrasive (cBN).

Most people's experiences are not ruling these factors out. They simply jump to conclusions with the name of the steel along with their idiosyncrasies of how they sharpen and interpret the sharpening.


Really the biggest difference was how they deburred which has more to do with matrix than carbides since cBN is harder than any carbide and effectively rules out differences in grindability of the edge bevel. The matrix is sensitive to heat treatment so that can be a factor for ease of deburring which is a factor for sharpenability.

Again they all got very sharp. It just goes to show the importance of good sharpening technique and abrasives along with the ability to assess and measure.
 
I must admit that I am not familliar with this terms of steel carateristics. Probably because I'm from Croatia. We have only two stages- sharp and dull.
Retention is when my Grandma honed knife on porcelan plate (bottom) and sharpness is when Grandpa stroped razor on belt. Sharpness and edge retention lasted all his life :)
 
zorandjurkic said:
I must admit that I am not familliar with this terms of steel carateristics. Probably because I'm from Croatia. We have only two stages- sharp and dull.
Retention is when my Grandma honed knife on porcelan plate (bottom) and sharpness is when Grandpa stroped razor on belt. Sharpness and edge retention lasted all his life :)
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It's a rabbit hole for sure!
 
Larrin said:
Recently I was able to acquire a used CATRA machine, so I heat treated just about every knife steel I had, made 57 knives with the help of knifemaker Shawn Houston, and tested them all to see which cut the longest. For a few of the steels I did multiple heat treatments to look at a couple variables and to see the effect of hardness. I also compared edge retention and toughness to see which steels have the best balance of properties. https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
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Hello Dr. Thomas! Would be REX121 have the best properties if it were hardened to 58 Hrc than other steels that are also hardened and heat treated to 58 Hrc? Thank You!
 
zorandjurkic said:
Hello Dr. Thomas! Would be REX121 have the best properties if it were hardened to 58 Hrc than other steels that are also hardened and heat treated to 58 Hrc? Thank You!
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Rex 121 has a very high volume of carbide and those carbides are very hard. So if all tested steels were at 58 Rc it would still be at the top or amongst the top steels.
 
zorandjurkic said:
Hello Dr. Thomas! Would be REX121 have the best properties if it were hardened to 58 Hrc than other steels that are also hardened and heat treated to 58 Hrc? Thank You!
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It would have the highest edge retention but the lowest toughness. The same would be true at any hardness. Going softer increases toughness slower for high carbide steels.

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