Under the microscope

[Clip]

Lansky fine diamond stone. I tried to pick out a few diamonds here and take a closer look at them.

50x



100x - first, matrix in focus; second, diamond on right in focus





200x - first, diamond on right; second, diamond on left





500x - first, diamond on right; second, diamond on left; third, diamond on left different focus







1000x - diamond on left, detail of surface

[Clip]

Lansky black hard Arkansas - not much to see here but a very fine grit stone. Because the surface of the stone was black and had a hard time reflecting light, I had to turn the light all the way up and open the aperture some too to let more light in. The wider aperture leads to a fuzzier picture, especially noticeable at 1000x

50x



100x



200x



500x



1000x

[Lagrangian]

Wow!!! So Cool!! Just beautiful... Thanks Clip!
I'll be looking over these again and again.

[jackknifeh]

Pictures of the diamond stones bring back memories. The diamond particles look like the stone on my wife's engagement ring.

About the edges. Very nice job of sharpening. The scratch patterns are consistant indicating very controlled and even strokes. I have read in the past when wanting a toothy edge the direction of the scratches was supposed to create a difference in cutting performance based on the direction of the scratches and the direction of cutting, heel to tip or tip to heel. The teeth on a saw blade are angled to cut on a forward stroke (tip to heel). The directions of the scratches was supposed to create the same thing. However looking at your edges I can't see any difference in the "teeth" when highly magnified. Would this be an episode on "Mythbusters"?

The pictures you are letting us see are definately enlightening. Like I've said before, your pictures show me what my beautiful edges really look like. You know when you look at a pretty girl across the club and then walk toward her, ... I better stop. It's the same story a girl told me about walking toward me.

Jack

[chuck_roxas45]

Awesome pics! Thanks!

[Lagrangian]

Hi Clip!

Thanks again for your micro-photos

Just a few questions about your metallographic microscope:
What kinds of lighting are you able to do?

(1) Bright-field lighting (If the sample were a mirror, the whole image would be bright white).
(2) Dark-field lighting (If the sample were a mirror, the whole image would be dark black).
(3) Polarized lighting (Sometimes not a feature on metallographic microscopes because metals do not polarize light upon reflection, however other materials like glass and diamonds do polarize(dielectrics).)
(4) Other (There are so many lighting and imaging schemes in optical microscopes, I hardly know them all.)

I'm also curious about what kind of aperature settings you have. Are the like f-stops on a camera?

If these are too technical to answer, don't mind me. I've been reading more and more about microscopes on Nikon's microscopy website (which is generally more focused on biological micropes):
http://www.microscopyu.com/

Sincerely,
--Lagrangian

P.S. We've always heard that obsidian flakes are incredibly sharp and smooth. Don't know if you have any obsidian around, but if get a chance, how about imaging the edge of a glass shard?

P.P.S. Ah, sorry for being so interested; if I had your microscope I'd probably spend all my free time taking pictures!

[Ferris Wheels]

Those are awesome pictures. Thanks for taking the time and effort to share these with us. I don't know about everyone else but this is very educational for me. Again thank you.

[MadRookie]

Clip:

You have just given edge photography a new dimension.....wow! those pics are awesome.

Now with equipment like that you must surely have the sharpest, geometry perfect edge in town...???!!!

Well done & thx for taking the time & effort to share!

[Kai Winters]

Thanks for the awesome pics and descriptions of what you are doing and how you are doing it.
I use the same system you use with the addition of the ultra-fine and blue sapphire ceramic hones for polishing.
I also have a mic in my lab, nowhere near your magnification nor imaging capabilities, and at higher mags I was not happy with the lack of smoothness along the edge of my knives. But after looking at your photos I am much less concerned. Edge perfection does not exist with our current setups and probably does not exist at all if you have high enough magnification hehehe.

I am now a Spyderco forum member thanks to your submissions and Lagrangian bringing this to us on the Blade Forums.

[jackknifeh]

Thanks for the awesome pics and descriptions of what you are doing and how you are doing it.
I use the same system you use with the addition of the ultra-fine and blue sapphire ceramic hones for polishing.
I also have a mic in my lab, nowhere near your magnification nor imaging capabilities, and at higher mags I was not happy with the lack of smoothness along the edge of my knives. But after looking at your photos I am much less concerned. Edge perfection does not exist with our current setups and probably does not exist at all if you have high enough magnification hehehe.

I am now a Spyderco forum member thanks to your submissions and Lagrangian bringing this to us on the Blade Forums.

Clip's pictures are pretty incredible. Don't forget who to blame for getting you sucked in to the forum. Welcome by the way.


Jack

[phillipsted]

Clip - these are great images. Thanks for sharing!

TedP

[Clip]

Hi Clip!

Thanks again for your micro-photos

Just a few questions about your metallographic microscope:
What kinds of lighting are you able to do?

(1) Bright-field lighting (If the sample were a mirror, the whole image would be bright white).
(2) Dark-field lighting (If the sample were a mirror, the whole image would be dark black).
(3) Polarized lighting (Sometimes not a feature on metallographic microscopes because metals do not polarize light upon reflection, however other materials like glass and diamonds do polarize(dielectrics).)
(4) Other (There are so many lighting and imaging schemes in optical microscopes, I hardly know them all.)

I'm also curious about what kind of aperature settings you have. Are the like f-stops on a camera?

If these are too technical to answer, don't mind me. I've been reading more and more about microscopes on Nikon's microscopy website (which is generally more focused on biological micropes):
http://www.microscopyu.com/

Sincerely,
--Lagrangian

P.S. We've always heard that obsidian flakes are incredibly sharp and smooth. Don't know if you have any obsidian around, but if get a chance, how about imaging the edge of a glass shard?

P.P.S. Ah, sorry for being so interested; if I had your microscope I'd probably spend all my free time taking pictures!

Lag, not a problem! I love trying to answer whatever you guys are throwing out there. Tomorrow I'll try to get some pictures of aluminum foil and some REAL polished samples so you all can actually see carbides.

The microscope is only set up for bright field lighting. I've got the ability to use Nomarski prisms to add contrast or depth to the image. I've tried to use it on the pictures I've been taking here, but unless the sample is flat I can't really tell a difference. If the sample is perfectly flat, it'll give something resembling topography like this:



The aperture setting is done by means of a sliding rod that controls the aperture blades. I wish it was set up more like the modern DSLRs, I think I'd be better able to control exposure and sharpness that way. I can add neutral density filters and one or two colored filters but not much else.

I've heard the same thing about obsidian. I don't have access to any unfortunately, nor glass shards. I'll look around for some other stuff to compare, or try to find some cheap obsidian on the 'bay.

Rookie, I like photography and knives, and I've been lucky enough that this is just an extension of both! As for the best edge in town, I'm feel like I'm using average sharpening equipment with good photography equipment, so I don't think I'm there yet. It'll take quite an investment to get optically perfect edges and I'm not willing to make that jump yet, as my knives cut the way I want them to the way I sharpen them currently. However, I also said that one knife is good enough, and you see how that turned out

Kai, I've been looking at getting the yellow and blue stones for a little while now, might have to pull the trigger on those soon. You're right about hardly ever achieving edge perfection, but they do feel like they hit cutting perfection sooner!

Thanks Josh, Jack, Ted!

Hopefully more pictures coming this week but I might be a little busier.

[Lagrangian]

Hi Clip,

Thanks for all the answers!
Hilarious as it is to say, I'm looking forward to some aluminum foil! lol

I'm no metallographist, but I remember hearing that metallographers first polish their sample until it is super flat and smooth, and then they etch the sample chemically. Carbides have different chemistry from the grains, which is also different from the grain boundaries, so these all etch differently. The chemical etch makes it easier to see these differences.

But, I think for what we're doing here, that would be a bit extreme.
Plus I wouldn't want to deal with nasty etching chemicals. ^_^;

Sincerely,
--Lagrangian

[Clip]

Hi Clip,

Thanks for all the answers!
Hilarious as it is to say, I'm looking forward to some aluminum foil! lol

I'm no metallographist, but I remember hearing that metallographers first polish their sample until it is super flat and smooth, and then they etch the sample chemically. Carbides have different chemistry from the grains, which is also different from the grain boundaries, so these all etch differently. The chemical etch makes it easier to see these differences.

But, I think for what we're doing here, that would be a bit extreme.
Plus I wouldn't want to deal with nasty etching chemicals. ^_^;

Sincerely,
--Lagrangian

Yes, we generally mount samples in Bakelite using heat and pressure to make it easier to work with. Then, hit it on 100 to 600 grit wet sandpaper to do the initial sanding. Afterward, it gets inserted into a holder for multiple samples, takes a spin on an automated polisher that works from 40 micron down to 0.5 micron suspensions. Afterward it gets etched using a variety of etchants that aren't too harsh if used correctly. And there are several etchants for things like iron-based metals, stainless steels, nickel and cobalt alloys and etc. In some/most samples it's difficult to see grain boundaries without first 'burning' or slightly etching one or more of the alloying elements.

I'd started a thread earlier looking for broken blades or hole cutouts so I could do a proper mount and polish and actually look at the grain structure/carbide formations. Didn't have any responses though, and I'm still considering what blades I can cut up. If anyone had a slice of steel from a knife they modified slightly that could work as well.

Edit: here is a very thorough list, but we only use nine or so frequently.
http://www.kaker.com/etch/demo/list/named.html

[Lagrangian]

Hi Clip,

Some of us mirror-polish our knife bevels with sub-micron grit. Probably not polished to the level of metallurgical studies, but I suppose they could be? Meaning, if one of us sent you a knife with a "mirror polished" edge, perhaps it wouldn't be much work for to you pick a point on the edge, and polish a spot to metallurgical levels, and then possibly etch and microscope it.

I have a Manix 2 in bd30p (basically s30v) that I wouldn't mind putting a mirror-edge on, and then parting with for awhile (all in the name of science! of course ). For me, it's a user knife, so if you were to put a small flat-spots in the edge, I wouldn't mind. Later, I would probably just re-profile the edge to grind out the flat-spots. If you are game for this, let me know. If you're able to shield the rest of the blade (with bakalite, or wax?), etching on the knife edge and bevel would be okay with me too. In other words, I don't mind edge damage that can be ground-out by reprofiling.

Another thing thing I wonder about is edge-wear, in particular I've always heard about "carbide tear-out," so I'm curious to actually see a microscope photo of it. I suppose it may be more prevelant in some steels than others. People (I think this includes Cliff Stamp) say that because the carbides are harder than the surrounding metal, they're a little like stones in concrete, and they can be ripped out of the knife edge. I suppose it depends on lots of stuff I don't know about (metallurgy). I'm guessing this will require etching to see. Anyways, if eventually, you were able to demonstrate this with microcscope photos, I think that would be awesome.

Sincerely,
--Lagrangian

[Clip]

Hi Clip,

Some of us mirror-polish our knife bevels with sub-micron grit. Probably not polished to the level of metallurgical studies, but I suppose they could be? Meaning, if one of us sent you a knife with a "mirror polished" edge, perhaps it wouldn't be much work for to you pick a point on the edge, and polish a spot to metallurgical levels, and then possibly etch and microscope it.

I have a Manix 2 in bd30p (basically s30v) that I wouldn't mind putting a mirror-edge on, and then parting with for awhile (all in the name of science! of course ). For me, it's a user knife, so if you were to put a small flat-spots in the edge, I wouldn't mind. Later, I would probably just re-profile the edge to grind out the flat-spots. If you are game for this, let me know. If you're able to shield the rest of the blade (with bakalite, or wax?), etching on the knife edge and bevel would be okay with me too. In other words, I don't mind edge damage that can be ground-out by reprofiling.

Another thing thing I wonder about is edge-wear, in particular I've always heard about "carbide tear-out," so I'm curious to actually see a microscope photo of it. I suppose it may be more prevelant in some steels than others. People (I think this includes Cliff Stamp) say that because the carbides are harder than the surrounding metal, they're a little like stones in concrete, and they can be ripped out of the knife edge. I suppose it depends on lots of stuff I don't know about (metallurgy). I'm guessing this will require etching to see. Anyways, if eventually, you were able to demonstrate this with microcscope photos, I think that would be awesome.

Sincerely,
--Lagrangian

If you get down to sub-micron levels, we should be able to see the grain structure and carbides in the steel once etched. I might be able to polish it further, but would have to be extremely careful as the final steps are rotating wheels with a PSA silk attached. This is what holds the suspended polishing compounds, and I'd hate to let the edge grab it and let it mess up the edge, wheel, or my fingers (not necessarily in that order).

Once it's polished finely enough, I'll take some etchant and apply with a q-tip. Plenty of control this way. If it's been sharpened to a mirror-edge already, I shouldn't have to flatten at all. The etchant will put a slight haze on the edge so it won't be as reflective, and should bring the carbides out. Also, it shouldn't affect anything that's not highly polished already, so once you get the knife back edge cleanup is easy as stropping a few times.

Carbide tear-out is pretty much exactly what you described. A softer matrix of alloy holds the harder carbides in place. When subject to sliding abrasion, the carbides can be ripped free of the base metal leaving small pockets or holes where they once were. I'm not sure if I could capture this on one of my knives, but I'll keep trying.

Here's an explanation on a larger scale. In the hardfacing business, welders sometimes use a MIG welder combined with a tungsten carbide feeder to weld an extremely abrasive, wear resistant deposit onto the edges or faces of high-wear parts. The MIG wire used becomes the matrix and the tungsten carbide particles are embedded while the weld pool is still molten but cooling. The matrix itself has carbides as well to strengthen the entire overlay. When done, the part usually looks like a mean sonofabitch (pictures off the internet):



And since the carbide is dropped into the molten pool, you get a cross-section that looks something like this:



This second picture is a laser deposit I think, and carbide density isn't near as high as I usually see.



When these are subject to high wear, the carbides can and will tear out of the matrix (leaving small voids), and the matrix will wear down to the next level of carbides. If I can't get a picture at the microscopic levels, hopefully this post could help explain it.

[Lagrangian]

Hi Clip,

Thanks! I like that example from welding. Very interesting!

I know that when metalshop guys say,"Tungsten Carbide" (say for a tungsten-carbide drill-bit) they really mean a metal-matrix composite of tungsten-carbide particles suspended in a cobalt matrix. The cobalt "wets" tungsten-carbide very well, and holds the particles together, like cement in concrete. I heard that cobalt isn't so good for jewlery, because it can corrode and leach out. So for tungsten-carbide jewlery, they replace the cobalt with nickel. Nickel is hard, and very corrosion resistant, and so is better for jewlery, whereas cobalt is better at wetting the tungsten-carbide and may also have other properties better for cutting metal.

Actually, to be honest, I'm trying to grind blade from a rectangular blank of tungsten-carbide. Dang that stuff is hard. So not sure I will succeed; after many hours of grinding on diamond stones, I've made less than a millimeter of progress, and might end up wearing out one of my diamond plates! Anyways, depending on how things go, I might ask if I can send you the tungsten carbide blank to look at as well.

I don't know the hardness of my tungsten blank, but a typical value for the grade I have is, a Rockwell A Hardness of around 90 (give or take). If you convert from Rockwell A hardness to Rockwell C Hardness, that gives approximately 75 HRC. For comparison, I've heard that a typical value for zirconia (used in ceramic knives) is somewhere around 70 HRC (although it varies depending on how the ceramic knife is manufactured, plus there is all that transformation-toughened zirconia, etc.).

Sincerely,
--Lagrangian

[Clip]

Hi Clip,

Thanks! I like that example from welding. Very interesting!

I know that when metalshop guys say,"Tungsten Carbide" (say for a tungsten-carbide drill-bit) they really mean a metal-matrix composite of tungsten-carbide particles suspended in a cobalt matrix. The cobalt "wets" tungsten-carbide very well, and holds the particles together, like cement in concrete. I heard that cobalt isn't so good for jewlery, because it can corrode and leach out. So for tungsten-carbide jewlery, they replace the cobalt with nickel. Nickel is hard, and very corrosion resistant, and so is better for jewlery, whereas cobalt is better at wetting the tungsten-carbide and may also have other properties better for cutting metal.

Actually, to be honest, I'm trying to grind blade from a rectangular blank of tungsten-carbide. Dang that stuff is hard. So not sure I will succeed; after many hours of grinding on diamond stones, I've made less than a millimeter of progress, and might end up wearing out one of my diamond plates! Anyways, depending on how things go, I might ask if I can send you the tungsten carbide blank to look at as well.

I don't know the hardness of my tungsten blank, but a typical value for the grade I have is, a Rockwell A Hardness of around 90 (give or take). If you convert from Rockwell A hardness to Rockwell C Hardness, that gives approximately 75 HRC. For comparison, I've heard that a typical value for zirconia (used in ceramic knives) is somewhere around 70 HRC (although it varies depending on how the ceramic knife is manufactured, plus there is all that transformation-toughened zirconia, etc.).

Sincerely,
--Lagrangian

The tungsten carbide in the example above is pure WC. Cast (virgin) or crushed/sintered (recycled) tungsten carbide, usually from 8x10 to 30x40 mesh sizes for the drop carbide applications. These measure approximately 2500-3000 HV. 75 HRC is approximately 1500 HV, so I'm guessing your plate isn't solid cast WC. If so, it would be incredibly hard and I'm not sure how fragile the edge would be. I've heard the same estimates for zirconia as well. Working at 75 HRC has got to be a PITA. I've had to grind stuff at 68-70 HRC and it took forever, so I feel your pain! Any pictures?

I was wondering if I could notch some steel stock (say 1/4 x 1/4 inch) along one side and then braze tungsten carbide inserts in similar to drill bits. After the rest of the work is done to turn the blank into a blade I think it'd look sort of like Kershaw's D2/13C26 blades. Might have to sharpen with diamond equipment, but it would be cool to see!

[Lagrangian]

Hi Clip,

Thanks for your reply.

My tungsten-carbide blank, is one used for metal-shop, so it is definitely one of the tungsten-carbide-cobalt types. (ie: not pure tungsten carbide.) The blank is often used to make jointer or planer blades in wood-shop, or used to make cutting bits in metal-shop.

My understanding is that a pure tungsten-carbide bit would be too brittle for metal-work. So they give up some hardness and gain some toughness by going to tungsten-carbide particles in a cobalt binder.
http://en.wikipedia.org/wiki/Cemented_carbide

Not that I actually know the details; I just read too many wikipedia articles and poke around science papers.

Sincerely,
--Lagrangian

[Clip]

Hi Clip,

Thanks for your reply.

My tungsten-carbide blank, is one used for metal-shop, so it is definitely one of the tungsten-carbide-cobalt types. (ie: not pure tungsten carbide.) The blank is often used to make jointer or planer blades in wood-shop, or used to make cutting bits in metal-shop.

My understanding is that a pure tungsten-carbide bit would be too brittle for metal-work. So they give up some hardness and gain some toughness by going to tungsten-carbide particles in a cobalt binder.
http://en.wikipedia.org/wiki/Cemented_carbide

Not that I actually know the details; I just read too many wikipedia articles and poke around science papers.

Sincerely,
--Lagrangian

Thanks for the info! I, too, spend a lot of time on Wikipedia We've had to work with some solid WC plates and they were awful about chipping/spalling. I wasn't aware that you could get blanks for those planer/jointer blades but now that I think about it, it's very obvious. Pictures of the aluminum foil to be posted tonight!