https://scienceofsharp.com/2024/01/18 ... n-15v/
Great SEM pics of carbide volume and edge fracture anaysis!
Science of sharp 15v analysis
-
Cycletroll
- Member
- Posts: 799
- Joined: Sun Oct 22, 2017 4:12 pm
- Location: North Central New Mexico
Science of sharp 15v analysis
Last edited by Cycletroll on Fri Jan 19, 2024 3:20 pm, edited 1 time in total.
Re: Science of sharp 15v analysis
Cool. Thanks for the link. Notice the new (to me) variable that Shawn has been underscoring of late: the hardness of the matrix. Also, very nice illustrations of the burr.
Steel novice who self-identifies as a steel expert. Proud M.N.O.S.D. member 0003. Spydie Steels: 4V, 15V, 20CV, AEB-L, AUS6, Cru-Wear, HAP40, K294, K390, M4, Magnacut, S110V, S30V, S35VN, S45VN, SPY27, SRS13, T15, VG10, XHP, ZWear, ZDP189
Re: Science of sharp 15v analysis
I always like seeing Todd's blog articles; his imaging is always top notch. I had a lot of thoughts about his study. Some of my thoughts and questions are critical of the study. Since Todd is a fellow man of science I figure I can write about those things publicly without hurting his feelings. It means I read his study very carefully and with great interest. Or since I don't think he visits Spyderco forum perhaps he won't read any of this anyway. I look forward to his future blog posts.
The main comparison was between a Victoronix knife and the Manix 2 in 15V. He found edge rolling in the Victorinox and micro-chipping in the 15V. This is perhaps obvious given that there is a major hardness difference between the two knives: the soft one rolled and the hard one chipped. However, I did have a lot of questions after reading through the details:
1) "With the blade thinned to 25 degrees, I moved to a Wicked Edge 1500 grit diamond hone at 14 degrees per side (28 inclusive). Unlike the DMT coarse, this diamond plate is abrasive, cutting both carbides and matrix, evidenced by the fact that whole carbides are visible among the abrasive striations."
I don't know what this paragraph is saying. The DMT plate didn't cut both carbides and matrix? Why would the plate being "abrasive" mean that it cuts both the carbides and matrix? In what way is the plate "abrasive" that is different than the DMT plate? Meaning there is a secondary abrasive apart from the diamond?
2) "To test the effectiveness of the keen edge, I repeated the same sisal rope cutting as was done with the factory edge. The first 20 or so cuts were practically effortless and cutting required increasingly more force as the edge degraded."
How much did the force increase over the course of the test? Was the force measured? Rope cutting can require relatively high forces when compared with many other common cutting tasks. How did the force at the end of 100 cuts differ between the Victorinox and Manix knives? Were any sharpness or cutting ability tests performed at the end of 100 cuts?
3) "The goal here is not to quantify edge retention, but to visualize the microscopic degradation of the knife edge. For comparison, I show a contrasting example of a the same 100 rope cuts using a simple steel Victorinox paring knife with a 'dual grit' edge prepared by Gabe Kirkwood (TheHomeSlice on youtube)."
Why use different sharpening of the two knives? Trying to isolate the behavior of a steel with two different edge geometries, and in this case two totally different sharpening methods, would be incredibly difficult. The "dual grit" method previously showed excellent results in slicing rope, and Todd says nothing about the edge angle differences between the two knives. A more acute angle may explain rolling in the Victorinox knife, for example. Since the dual grit method led to greatly enhanced edge retention in prior rope cutting tests, I would be concerned that the failure mode is changed, which is the main thing being analyzed in this current study.
4) "Unlike the 15V steel, the softer Victorinox displays deformation and a large roll. Both the microchips in the 15V and the roll in the Victorinox impede the slicing performance, even though they constitute just fraction of the cutting edge. The microchipped 15V will retain some slicing aggression due to the carbide texture. The surface of the roll is dead-smooth. In normal use we could simply avoid this part of the edge and continue to cut well beyond 100 slices. Again, I am not trying to quantify edge retention, only identify the failure modes. The 15V blade shows no evidence of mushrooming or rolling, certainly due to the high hardness of the matrix."
He stated that he is not quantifying edge retention, only identifying failure modes. But the performance of something matters apart from its failure mode, sometimes more so (depending on how catastrophic the failure is and in what context). If the one knife is capable of 1000 cuts while the other is capable of 20, the failure mode is relevant and interesting, though we would probably favor the failure mode leading to 1000 cuts vs the failure mode leading to 20. The rolling of the Victorninox was bad enough to "impede the slicing performance" while the 15V chipping still retained "some slicing aggression" which might also lead us to favor one failure mode over another. Testing slicing sharpness can be difficult but if that could be quantified it would help in the interpretation. Because ultimately it is the quantifiable performance that matters, regardless of what it looks like. What it looks like on a microscopic scale can help us to learn why it behaved how it did, but doesn't necessarily tell us how it behaved.
4) "The wear resistance imparted by the high carbide volume prevents blunting via abrasion. Failure seems to occur through chipping as with other high carbide steels, eventually leaving a rough, squared-off ceramic knife type edge."
"I see little evidence of abrasive wear contributing to edge deterioration, suggesting that traditional CATRA testing (using silica impregnated cardstock) may not be particularly informative for this class of steels."
He has images of before and after in a "blunted" region of the 15V knife that shows that the edge radius increased over the course of the test. So significant abrasive wear appears to have occurred, leading me to be confused about why he says that abrasive wear was not a factor. He also makes relatively broad statements about high carbide steel performance even though he described his test as seeing "whether this steel can take and hold a relatively fine edge with usage that would be considered abusive for a high-end kitchen knife, but considered light duty for a bushcraft/survival knife." So if the use is "abusive" for a kitchen knife, then there may be certainly be applications where microchipping is significantly less than what he observed. ZDP-189 is very popular in kitchen knives and many users report outstanding edge retention with their knives. The 15V microchipping observed was also said to be "just [a] fraction of the cutting edge."
So it is not clear how widespread the microchipping was, and whether it would be a problem in all cutting scenarios. 15 dps with a fixed angle sharpening system is pretty acute overall, plus the relatively high forces applied in rope cutting, mean that more obtuse edges or other cutting tasks may lead to different behavior. The benefit and detriment of doing an uncontrolled, specific test is that there is mixed-mode behavior. Meaning a combination of uneven, sometimes high, forces, and abrasive wear. But another cutting test or another edge geometry would show different behavior. A sufficiently obtuse edge would presumably not see edge rolling or chipping and would see only wear. Mixed-mode tests are very useful for seeing how things will combine together, but one test doesn't always apply to another.
On the opposite end of the spectrum are tests that look at one individual behavior: CATRA for edge wear, hardness for resistance to deformation, impact toughness for resistance to fracture, and various corrosion tests (because sharpness loss can be from corrosion as well, especially when cutting acidic foods or in a saltwater environement). Even CATRA can have confounding factors such as edge geometry and sharpening being much larger effects than the steel or even the heat treatment. When you have information from the three different test types (wear, deformation, and toughness), you can select different steels or heat treatments after observing failure modes in a mixed-mode test. So if the knife chipped you would look at a higher toughness steel, if you saw wear you would like at higher wear resistance steels, if you saw deformation you would look at a higher hardness heat treatment or a steel that can reach a higher hardness. But again this is specific to the test being performed. A different test with different edge geometry would have a different failure mode and thus have a different priority for which properties are more important than others.
5) "The 30 degree inclusive edge performs well with moderate cutting tasks like rope and cardboard, but not surprisingly does chip when subjected to riskier usage such as cutting 14 gauge copper wire (shown below). A knife is not the appropriate tool for that task, particularly one that is not readily replaceable. The image below show a good sized chip that was formed while cutting the copper wire."
Or if the test performed is subjecting even higher forces to the knife, then abrasive wear doesn't matter at all, as he showed by cutting copper wire. Of course we wouldn't necessarily conclude that wear resistance doesn't matter for knives, but that in this type of cutting the knife had insufficient toughness for the task and edge geometry.
6) "As with the other high carbide steels (K390, Maxamet, S110V) I see little evidence of abrasive wear contributing to edge deterioration."
While it can be easy to suggest that "more testing is required," I would like to see a test comparison with a knife that had similar hardness in a low carbide steel. With the same sharpening this time, of course. That would show whether it is possible to achieve a purely abrasive wear mode of failure as opposed to rolling or chipping. Sharpness loss is always going to be relatively rapid if gross failure is being observed. A low carbide steel of higher hardness would either confirm Todd's apparent preference for low carbide steels, or show that the edge geometry is insufficient for the rope cutting task being performed.
Conclusions
It is very rare to get such excellent SEM images of knives with different steel, different sharpening methods, and after different uses. I hope Todd keeps doing his fun studies!
The main comparison was between a Victoronix knife and the Manix 2 in 15V. He found edge rolling in the Victorinox and micro-chipping in the 15V. This is perhaps obvious given that there is a major hardness difference between the two knives: the soft one rolled and the hard one chipped. However, I did have a lot of questions after reading through the details:
1) "With the blade thinned to 25 degrees, I moved to a Wicked Edge 1500 grit diamond hone at 14 degrees per side (28 inclusive). Unlike the DMT coarse, this diamond plate is abrasive, cutting both carbides and matrix, evidenced by the fact that whole carbides are visible among the abrasive striations."
I don't know what this paragraph is saying. The DMT plate didn't cut both carbides and matrix? Why would the plate being "abrasive" mean that it cuts both the carbides and matrix? In what way is the plate "abrasive" that is different than the DMT plate? Meaning there is a secondary abrasive apart from the diamond?
2) "To test the effectiveness of the keen edge, I repeated the same sisal rope cutting as was done with the factory edge. The first 20 or so cuts were practically effortless and cutting required increasingly more force as the edge degraded."
How much did the force increase over the course of the test? Was the force measured? Rope cutting can require relatively high forces when compared with many other common cutting tasks. How did the force at the end of 100 cuts differ between the Victorinox and Manix knives? Were any sharpness or cutting ability tests performed at the end of 100 cuts?
3) "The goal here is not to quantify edge retention, but to visualize the microscopic degradation of the knife edge. For comparison, I show a contrasting example of a the same 100 rope cuts using a simple steel Victorinox paring knife with a 'dual grit' edge prepared by Gabe Kirkwood (TheHomeSlice on youtube)."
Why use different sharpening of the two knives? Trying to isolate the behavior of a steel with two different edge geometries, and in this case two totally different sharpening methods, would be incredibly difficult. The "dual grit" method previously showed excellent results in slicing rope, and Todd says nothing about the edge angle differences between the two knives. A more acute angle may explain rolling in the Victorinox knife, for example. Since the dual grit method led to greatly enhanced edge retention in prior rope cutting tests, I would be concerned that the failure mode is changed, which is the main thing being analyzed in this current study.
4) "Unlike the 15V steel, the softer Victorinox displays deformation and a large roll. Both the microchips in the 15V and the roll in the Victorinox impede the slicing performance, even though they constitute just fraction of the cutting edge. The microchipped 15V will retain some slicing aggression due to the carbide texture. The surface of the roll is dead-smooth. In normal use we could simply avoid this part of the edge and continue to cut well beyond 100 slices. Again, I am not trying to quantify edge retention, only identify the failure modes. The 15V blade shows no evidence of mushrooming or rolling, certainly due to the high hardness of the matrix."
He stated that he is not quantifying edge retention, only identifying failure modes. But the performance of something matters apart from its failure mode, sometimes more so (depending on how catastrophic the failure is and in what context). If the one knife is capable of 1000 cuts while the other is capable of 20, the failure mode is relevant and interesting, though we would probably favor the failure mode leading to 1000 cuts vs the failure mode leading to 20. The rolling of the Victorninox was bad enough to "impede the slicing performance" while the 15V chipping still retained "some slicing aggression" which might also lead us to favor one failure mode over another. Testing slicing sharpness can be difficult but if that could be quantified it would help in the interpretation. Because ultimately it is the quantifiable performance that matters, regardless of what it looks like. What it looks like on a microscopic scale can help us to learn why it behaved how it did, but doesn't necessarily tell us how it behaved.
4) "The wear resistance imparted by the high carbide volume prevents blunting via abrasion. Failure seems to occur through chipping as with other high carbide steels, eventually leaving a rough, squared-off ceramic knife type edge."
"I see little evidence of abrasive wear contributing to edge deterioration, suggesting that traditional CATRA testing (using silica impregnated cardstock) may not be particularly informative for this class of steels."
He has images of before and after in a "blunted" region of the 15V knife that shows that the edge radius increased over the course of the test. So significant abrasive wear appears to have occurred, leading me to be confused about why he says that abrasive wear was not a factor. He also makes relatively broad statements about high carbide steel performance even though he described his test as seeing "whether this steel can take and hold a relatively fine edge with usage that would be considered abusive for a high-end kitchen knife, but considered light duty for a bushcraft/survival knife." So if the use is "abusive" for a kitchen knife, then there may be certainly be applications where microchipping is significantly less than what he observed. ZDP-189 is very popular in kitchen knives and many users report outstanding edge retention with their knives. The 15V microchipping observed was also said to be "just [a] fraction of the cutting edge."
So it is not clear how widespread the microchipping was, and whether it would be a problem in all cutting scenarios. 15 dps with a fixed angle sharpening system is pretty acute overall, plus the relatively high forces applied in rope cutting, mean that more obtuse edges or other cutting tasks may lead to different behavior. The benefit and detriment of doing an uncontrolled, specific test is that there is mixed-mode behavior. Meaning a combination of uneven, sometimes high, forces, and abrasive wear. But another cutting test or another edge geometry would show different behavior. A sufficiently obtuse edge would presumably not see edge rolling or chipping and would see only wear. Mixed-mode tests are very useful for seeing how things will combine together, but one test doesn't always apply to another.
On the opposite end of the spectrum are tests that look at one individual behavior: CATRA for edge wear, hardness for resistance to deformation, impact toughness for resistance to fracture, and various corrosion tests (because sharpness loss can be from corrosion as well, especially when cutting acidic foods or in a saltwater environement). Even CATRA can have confounding factors such as edge geometry and sharpening being much larger effects than the steel or even the heat treatment. When you have information from the three different test types (wear, deformation, and toughness), you can select different steels or heat treatments after observing failure modes in a mixed-mode test. So if the knife chipped you would look at a higher toughness steel, if you saw wear you would like at higher wear resistance steels, if you saw deformation you would look at a higher hardness heat treatment or a steel that can reach a higher hardness. But again this is specific to the test being performed. A different test with different edge geometry would have a different failure mode and thus have a different priority for which properties are more important than others.
5) "The 30 degree inclusive edge performs well with moderate cutting tasks like rope and cardboard, but not surprisingly does chip when subjected to riskier usage such as cutting 14 gauge copper wire (shown below). A knife is not the appropriate tool for that task, particularly one that is not readily replaceable. The image below show a good sized chip that was formed while cutting the copper wire."
Or if the test performed is subjecting even higher forces to the knife, then abrasive wear doesn't matter at all, as he showed by cutting copper wire. Of course we wouldn't necessarily conclude that wear resistance doesn't matter for knives, but that in this type of cutting the knife had insufficient toughness for the task and edge geometry.
6) "As with the other high carbide steels (K390, Maxamet, S110V) I see little evidence of abrasive wear contributing to edge deterioration."
While it can be easy to suggest that "more testing is required," I would like to see a test comparison with a knife that had similar hardness in a low carbide steel. With the same sharpening this time, of course. That would show whether it is possible to achieve a purely abrasive wear mode of failure as opposed to rolling or chipping. Sharpness loss is always going to be relatively rapid if gross failure is being observed. A low carbide steel of higher hardness would either confirm Todd's apparent preference for low carbide steels, or show that the edge geometry is insufficient for the rope cutting task being performed.
Conclusions
It is very rare to get such excellent SEM images of knives with different steel, different sharpening methods, and after different uses. I hope Todd keeps doing his fun studies!
http://www.KnifeSteelNerds.com - Steel Metallurgy topics related to knives
-
Albertaboyscott
- Member
- Posts: 337
- Joined: Mon Sep 24, 2018 8:13 am
Re: Science of sharp 15v analysis
Awesome pictures. Carbides look like little eggs in that one shot
Re: Science of sharp 15v analysis
The pictures were excellent, the analysis did seem kind of wandering and aimless.
-
cholla_remover
- Member
- Posts: 89
- Joined: Fri Dec 03, 2021 11:09 pm
Re: Science of sharp 15v analysis
I enjoyed the original article and the counter-analysis here. Good thread
Re: Science of sharp 15v analysis
I just came here to ask what wireless usb microscope did he pick up off of Amazon? His images look a bit better than the ones my $30 version produces.
- Jeff
May your feet be warm and dry and your throat warm with whiskey. A knife in hand or in the sock band.
MNOSD Member #0005
May your feet be warm and dry and your throat warm with whiskey. A knife in hand or in the sock band.
MNOSD Member #0005
Re: Science of sharp 15v analysis
Ha!
http://www.KnifeSteelNerds.com - Steel Metallurgy topics related to knives
-
Josh Crutchley
- Member
- Posts: 1395
- Joined: Wed Sep 30, 2020 2:44 am
- Location: Michigan
Re: Science of sharp 15v analysis
I got caught up by that part as well. It was a coarse DMT so wouldn't alot of the carbide just be plowed away with the matrix? The WE plate was higher grit and wouldn't be able to plow through the carbides like the coarse DMT.Larrin wrote: ↑Thu Jan 18, 2024 7:41 pm
1) "With the blade thinned to 25 degrees, I moved to a Wicked Edge 1500 grit diamond hone at 14 degrees per side (28 inclusive). Unlike the DMT coarse, this diamond plate is abrasive, cutting both carbides and matrix, evidenced by the fact that whole carbides are visible among the abrasive striations."
I don't know what this paragraph is saying. The DMT plate didn't cut both carbides and matrix? Why would the plate being "abrasive" mean that it cuts both the carbides and matrix? In what way is the plate "abrasive" that is different than the DMT plate? Meaning there is a secondary abrasive apart from the diamond?
-
Deadboxhero
- Member
- Posts: 2178
- Joined: Tue Mar 01, 2016 4:35 am
- Contact:
Re: Science of sharp 15v analysis
Extraordinary images by Todd Simpson.
And that was an excellent analysis by Dr Larrin.
What a fantastic treat for us all.
And that was an excellent analysis by Dr Larrin.
What a fantastic treat for us all.
-
Deadboxhero
- Member
- Posts: 2178
- Joined: Tue Mar 01, 2016 4:35 am
- Contact:
Re: Science of sharp 15v analysis
Thank you, What did you think about the images?ekastanis wrote: ↑Fri Jan 19, 2024 6:20 pm“Dr Todd”
https://www.researchgate.net/profile/Todd-Simpson-3
Re: Science of sharp 15v analysis
Todd does great work. A real asset to the knife community. especially for the "Edge Junky's".
sal
sal
Re: Science of sharp 15v analysis
I am not on a level that would let me join the actual discussion - still I want to say :Very interesting read! (Both the article and this thread).
Top three going by pocket-time (update March 24):
- EDC: Endura thin red line ffg combo edge (VG10); Wayne Goddard PE (4V), Endela SE (VG10)
-Mountains/outdoors: Pac.Salt 1 SE (H1), Salt 2 SE (LC200N), and also Wayne Goddard PE (4V)
- EDC: Endura thin red line ffg combo edge (VG10); Wayne Goddard PE (4V), Endela SE (VG10)
-Mountains/outdoors: Pac.Salt 1 SE (H1), Salt 2 SE (LC200N), and also Wayne Goddard PE (4V)
Re: Science of sharp 15v analysis
The images are excellent as usual from Science of Sharp. Always particularly interesting to me is the sectioning of the edge by focused ion beam, and more recently the elemental analysis by EDS. This photo set and its subject steel might be the most captivating yet. We're very fortunate to benefit from someone with the expertise, access to facilities, and standing at an organization that allows him to apply all this to a hobby of his, and equally so that experts in metallurgy and knife making are able to share their analysis. Who could have imagined ten years ago that everyone would have access to such insight?
-
Deadboxhero
- Member
- Posts: 2178
- Joined: Tue Mar 01, 2016 4:35 am
- Contact:
Re: Science of sharp 15v analysis
Very well said, thank you for sharing.ekastanis wrote: ↑Sat Jan 20, 2024 9:19 amThe images are excellent as usual from Science of Sharp. Always particularly interesting to me is the sectioning of the edge by focused ion beam, and more recently the elemental analysis by EDS. This photo set and its subject steel might be the most captivating yet. We're very fortunate to benefit from someone with the expertise, access to facilities, and standing at an organization that allows him to apply all this to a hobby of his, and equally so that experts in metallurgy and knife making are able to share their analysis. Who could have imagined ten years ago that everyone would have access to such insight?
Re: Science of sharp 15v analysis
I Wonder if Todd would be interested in playing with one of the new HIC ceramic Mule Team? I've asked him to join our forum, but he's pretty busy.
Hey Shawn, Larrin, Might you GUYS be interested in playing with One? A ceramic "Sport Knife" in a "new" ceramic? I know it's not steel, which is the first love, but curiosity as to what it is and where can it go does have a draw?
W'eve got sorry really bright folks hanging here that we can learn from.
Hegel said that Progress is made in the following format; There is an idea, which becomes the "thesis". Because of the existence of the thesis, there develops an Antithesis. The the thesis and Antithesis combine to form a Synthesis which is the best of the two (thesis and antithesis).
Could ceramic be the Antithesis of steel for blades?
sal
Hey Shawn, Larrin, Might you GUYS be interested in playing with One? A ceramic "Sport Knife" in a "new" ceramic? I know it's not steel, which is the first love, but curiosity as to what it is and where can it go does have a draw?
W'eve got sorry really bright folks hanging here that we can learn from.
Hegel said that Progress is made in the following format; There is an idea, which becomes the "thesis". Because of the existence of the thesis, there develops an Antithesis. The the thesis and Antithesis combine to form a Synthesis which is the best of the two (thesis and antithesis).
Could ceramic be the Antithesis of steel for blades?
sal