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Todd Simpson has just posted a fascinating series of scanning electron microscope edge images of a Maxamet Native 5, sharpened with different techniques and abrasives.

Check it out, and let’s start a conversation here.

https://scienceofsharp.com/2019/11/03/c ... n-maxamet/

Interesting; so essentially, carbides (in Maxamet anyway) do not "tear out", either through normal sharpening or normal use?

Thank you, Cambertree. For sharing this with us here!

Excellent article with some interesting insights.

JonLeBlanc wrote: ↑

Sun Nov 03, 2019 6:57 pm

Interesting; so essentially, carbides (in Maxamet anyway) do not "tear out", either through normal sharpening or normal use?

It appears that way, Jon - in this sample at least.

One question which I’d be very interested to see more research or explanation about by the experts, is the relation between different carbides and the steel matrix.

In my laymans experience and sharpening of the cobalt containing steels like VG10, CPM M4, HAP40 and Maxamet et al, it almost seems as if the edges are more uniform, like the carbides are bound more strongly into the matrix.

Conversely, some ‘simple’ stainlesses with the large chromium carbide predominating in a softer matrix, can feel a little ‘brittle’ at the edge on the finer stones.

Whether those are actual effects or just my skewed perception, I don’t know.

SteveMidwest wrote: Thank you, Cambertree. For sharing this with us here!

Thanks Steve, there’s some really excellent material being put out at the moment. :)

blues wrote: ↑

Sun Nov 03, 2019 7:18 pm

Excellent article with some interesting insights.

Yeah, I found those images of Maxamet which had had the matrix abraded at the edge by alumina oxide or natural Japanese waterstones particularly fascinating. Lots of tiny protruding carbide ‘teeth’.

Larger carbides are more likely to fracture or separate from the matrix from applied stress. The article provides some fun images for sure. I wouldn't say that it shows that carbides do not "tear out" however. The images are showing the carbides that didn't fall out, obviously. He is more demonstrating that many carbides are still there. He seems to be arguing against those that say that all of them easily fall out I guess. I didn't know that is a popular opinion.

I'd be curious what the result would have been had a Spyderco medium ceramic rod or bench stone been used in place of the Shapton or JNat.

I'm also curious at what angle the micro bevel was applied following the 17 degree sharpening and the 17.5 degree polish with the diamond lapping film.

Great article and really cool photos!

Thanks for sharing Cambertree!

Very interesting material. I've tried looking at my edges with a jewelers loupe before, but I'll just stop that now.

Larrin wrote: ↑

Sun Nov 03, 2019 7:35 pm

Larger carbides are more likely to fracture or separate from the matrix from applied stress. The article provides some fun images for sure. I wouldn't say that it shows that carbides do not "tear out" however. The images are showing the carbides that didn't fall out, obviously. He is more demonstrating that many carbides are still there. He seems to be arguing against those that say that all of them easily fall out I guess. I didn't know that is a popular opinion.

However, the carbides remained in place through both use and sharpening, the very instances in which some have expected carbides to be torn from the edge.

Like Larrin said, the pictures show the carbides that didn't fall out. I would say this debunks anything really.

I also don't like his answer to the comment at the bottom saying for slicing agression, exposing the carbides is an obvious approach. Tell that to my DMT coarse and extra coarse stones. No need to kill the slicing agression by using an alumina based abrasive to "expose carbides". His view of slicing agression is much different than mine. I'd like to hand him a 5 inch thick synthetic rope and see how his carbides do, lol.

I would think (especially based on the latter images in the article) that the carbides exposed along the edge would be more susceptible to lateral forces.

a more apt comparison to the concrete would look for gravel tearout on especially sharp curbs?

I'm not sure if the tearout concern is being worried about carbides being removed from the bevel behind the edge itself, or carbides being torn away from the matrix. Thoughts?

Thank for sharing the article Cambertree!

To paraphrase Cliff Stamp: When you sharpen CPM 10V on India stone, it´s not going to suddenly behave like there is no carbides at all.

My thinking is, that even with high carbides steel, if some carbide tear-out happend, it does not bother me at grit level that I am sharpening. My highest grit stone is Spyderco medium ceramic, and particles in stone are much much larger then carbides in PM steels.
So I think that until some level of grit you are not going to see much of a difference in edge holding between diamond/CNB abrasive vs ceramic/SiC.

And even after sharpening with 8k water stone, there were still carbides on the edge, like they are there, they did not just fell out to nirvana.

The article was helpful for me for two reasons.

One, it introduces the idea of finishing the apex with a softer Al2O3 Stone to clear some matrix off the carbides after first apexing with diamonds. Voilá! Micro serrations! (I can see how even larger serrations are better for tough rope or French bread. If you consider a shark’s rows of teeth, there are serrations at several different size scales simultaneously. We can attain a similar dynamic by taking a carbide-rich alloy, grinding in a serration pattern, then apexing at a coarse grit. This’ll give teeth at three different size ranges. Very interesting.)

Two, it presents a compelling visual image that shows a feather edge burr is not helpful to cutting performance.

Thank you for sharing this.

My interpretation of given data is different than the author/Todd of linked page/article. Obviously conclusion would also different.

Finally had to touch up my Mule Team, haven't had to deal with it since I tested it years ago. Started to hang some on phone book paper.

Use it for opening boxes etc...

Stropped it a little on my SIC loaded strop and that was it.

Not sure what point the article is making but love the pictures.

As for Maxamet, I used my Mule to cut up boxes for hours. Had a mountain of them after a cross country move. All I can say is that whatever it is doing with it's carbides, it's doing it really well.

Larger carbides are more likely to fracture or separate from the matrix from applied stress. The article provides some fun images for sure. I wouldn't say that it shows that carbides do not "tear out" however. The images are showing the carbides that didn't fall out, obviously. He is more demonstrating that many carbides are still there. He seems to be arguing against those that say that all of them easily fall out I guess. I didn't know that is a popular opinion.

It has been repeated as a truth especially on bladeforums for years now. It's one of those things that everybody "knows".

I was wondering how 440C or D2 would do in these tests. I've seen examples of these two steels that have carbide banding and pretty large carbides compared to the powder steels we take for granted now.

Joe

The Mastiff wrote: ↑

Mon Nov 04, 2019 4:17 pm

Larger carbides are more likely to fracture or separate from the matrix from applied stress. The article provides some fun images for sure. I wouldn't say that it shows that carbides do not "tear out" however. The images are showing the carbides that didn't fall out, obviously. He is more demonstrating that many carbides are still there. He seems to be arguing against those that say that all of them easily fall out I guess. I didn't know that is a popular opinion.

It has been repeated as a truth especially on bladeforums for years now. It's one of those things that everybody "knows".

I was wondering how 440C or D2 would do in these tests. I've seen examples of these two steels that have carbide banding and pretty large carbides compared to the powder steels we take for granted now.

Joe

There is an image of carbide pullout in this article: https://knifesteelnerds.com/2018/06/18/ ... retention/

It was much more apparent in 154CM than CPM-154.