Photo micrographs

Thanks Larrin. At least I understand them !! That last one shows perfactly how the matrix will wear away leaving the carbides 'exposed'.
 
Can someone explain a little bit about the general features seen and give a brief synopsis of what these mean?

From what I can tell (just guessing really) S30V looks like it would perform really well in both toughness and edge retention.
 
therulebookman said:
Can someone explain a little bit about the general features seen and give a brief synopsis of what these mean?

From what I can tell (just guessing really) S30V looks like it would perform really well in both toughness and edge retention.
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You made that out of those pictures? How?
 
Larrin, Here is the response I gave to your thread on the reviews and testing forum. Looks like more folks are responding over here so I'll copy them to here.

COOL!!!
Awesome shots. Really puts things in perspective.

What magnification is that?
Are all the shots at the same mag?
Are these electron micrographs?
Were these from blades, or were these from sheet stock?
Have you seen differences between samples of the same alloy with different heat treats?

Thanks for sharing these with us. The old aphorism is true. One pic is worth 1,000 words. That would make this post equivalent to a 10,000 word dissertation.
 
knarfeng said:
Larrin, Here is the response I gave to your thread on the reviews and testing forum. Looks like more folks are responding over here so I'll copy them to here.

COOL!!!
Awesome shots. Really puts things in perspective.

What magnification is that?
Are all the shots at the same mag?
Are these electron micrographs?
Were these from blades, or were these from sheet stock?
Have you seen differences between samples of the same alloy with different heat treats?

Thanks for sharing these with us. The old aphorism is true. One pic is worth 1,000 words. That would make this post equivalent to a 10,000 word dissertation.
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I didn't take the pictures, so I can't answer all of your questions, but I can try. They are all the same magnification except the pictures of the edges. I don't think they are electron micrographs.

I wish I knew more about the worn edges, it is a pretty old picture (before 1990), so the specifics might be lost to even Sandvik.

The same alloy with different heat treatments would look different, higher austenitizing temperatures dissolve more carbide, for example.
 
PatriotDan said:
You made that out of those pictures? How?
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I think you quoted me as saying "mainly guessing" but I deduced that conclusion based partially on what I have heard, but also kind of like this:

If someone falls and scrapes their knee on dirty ground there will be little peices of dirt in there, some larger than others. when cleaning it, its much easier to get out the big peices than the small peices...and all of the pictures have more big pieces than small peices in comparison with s30v. (edge retention) also, the s30v picture looks like its made up of alot of tiny particles densely packed, similarly to the way High-Density Fiberboard is packed with lots of tiny particles and its alot stronger than Low-Density Fiberboard which has bigger peices less densely packed. (toughness)

the reason its a guess is I have no idea whether these principles apply to steel. Thats why I asked someone to explain it. Its always fun to speculate:D
 
therulebookman said:
I think you quoted me as saying "mainly guessing" but I deduced that conclusion based partially on what I have heard, but also kind of like this:

If someone falls and scrapes their knee on dirty ground there will be little peices of dirt in there, some larger than others. when cleaning it, its much easier to get out the big peices than the small peices...and all of the pictures have more big pieces than small peices in comparison with s30v. (edge retention) also, the s30v picture looks like its made up of alot of tiny particles densely packed, similarly to the way High-Density Fiberboard is packed with lots of tiny particles and its alot stronger than Low-Density Fiberboard which has bigger peices less densely packed. (toughness)

the reason its a guess is I have no idea whether these principles apply to steel. Thats why I asked someone to explain it. Its always fun to speculate:D
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Toughness is greatly controlled by the amount and size of carbide. The smaller the volume and the smaller the carbides, the greater the toughness. There are other factors, such as amount of carbon and other alloys in the matrix, as well as impurity, but carbides greatly control toughness.

Edge retention is a little trickier. Edge retention is controlled by strength (preventing rolling), toughness (preventing chipping and micro-chipping), wear resistance, the size of the carbides, and sometimes corrosion. The larger the volume and the larger the amount of carbide, the greater the wear resistance, but with knife edges, the smaller the carbides, the better the edge retention, especially with fine edges. The trick with knife edges is we want the greatest amount of wear resistance with the smallest possible carbide size. Vanadium carbides are very hard, so they contribute more to wear resistance than chromium carbides, so a smaller volume of vanadium carbide can have the same wear resistance as a larger volume of chromium carbide. This is why Crucible uses vanadium, so they can have the greatest amount of wear resistance for the smallest amount of carbide. However, with PM steels, the larger the volume of a particular type of carbide, the larger those carbides get, but different kinds generally don't combine with others, so sometimes I wish they would develop alloys using a variety of carbide types to maximize wear resistance and carbide size, though grades like CPM-M4 do this to a degree.
 
cds4byu said:
Nice photos.

How were the edges worn?

Carl
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They told me that they cut some kind of abrasive material, I think it was some kind of man-made material rope. The pictures of the edges are pretty old.
 
Porn for metallurgists!

I start a class about microstructures in 2 weeks, it'S going to be fun:)
 
Excellent pictures, thanks for posting. Any idea about heat treat/hardness of the samples? I think it would be a little hard to make too many assumptions w/o knowing this.
 
Blue Sky said:
Excellent pictures, thanks for posting. Any idea about heat treat/hardness of the samples? I think it would be a little hard to make too many assumptions w/o knowing this.
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I don't know how they heat treated them. Roman Landes told me that the photo micrographs look similar to those he's taken of the same steels, but I can e-mail Sandvik and ask them how they heat treated them if you want.
 
Larrin said:
Photo micrographs of various steels, and two worn knife edges, one from 440C and one from 13C26: http://www.fototime.com/inv/00BD612B8194CE6
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Are you author of this pictures? I like to post them on my web site if this possible. Pleae, allow me. Do you have any comment. I guess it worse to make some kind of article around them, I can post it on my website in English and I can translate in Russinan too.

Thanks, Vassili.
 
The last 2 pictures are probably SEM (Scanning Electron Microscope) photomicrographs, since they show surfaces or micro-topography so well.

Eons ago, when I did petrography, we used the term photomicrographs for shots of thin sections under plane polarized light. I am only speculating, but since steels are probably opaque, they're using a reflecting microscope (polished sections) wherein the light bounces off of the polished surface of the sample (and not refracted through it as happens for petrographic microscopy). The clear outlines are the harder grains that don't erode as easily when the slide was polished, and I think (hazy recall from my enfeebled brain), the brighter grains are opaque phases such as iron oxides. Or they just stand out because they protruded and polished flatter compared to the surround matrix. This is just speculation using some of the lab microscopy from a background in geochemistry :D , and may not accurately reflect man-made materials and metallurgy. The systematics of interpretation gotta be different when examining steels.
 
nozh2002 said:
Are you author of this pictures? I like to post them on my web site if this possible. Pleae, allow me. Do you have any comment. I guess it worse to make some kind of article around them, I can post it on my website in English and I can translate in Russinan too.

Thanks, Vassili.
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I did not take the pictures. The Sandvik metallurgists told me I could use the pictures for whatever I want, but I don't know about you using them; e-mail me and I will give you their e-mail addresses. Also, I wrote quite a bit about the micrographs and edge theory here: http://www.knifeforums.com/forums/showtopic.php?tid/797292/tp/1/ but it would be a lot better if it were in a better order and nice and organized if you wanted to have an actual article.
 
Ultraman said:
The last 2 pictures are probably SEM (Scanning Electron Microscope) photomicrographs, since they show surfaces or micro-topography so well.

Eons ago, when I did petrography, we used the term photomicrographs for shots of thin sections under plane polarized light. I am only speculating, but since steels are probably opaque, they're using a reflecting microscope (polished sections) wherein the light bounces off of the polished surface of the sample (and not refracted through it as happens for petrographic microscopy). The clear outlines are the harder grains that don't erode as easily when the slide was polished, and I think (hazy recall from my enfeebled brain), the brighter grains are opaque phases such as iron oxides. Or they just stand out because they protruded and polished flatter compared to the surround matrix. This is just speculation using some of the lab microscopy from a background in geochemistry :D , and may not accurately reflect man-made materials and metallurgy. The systematics of interpretation gotta be different when examining steels.
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Change your theories to fit the fact that the white spots are carbides, and you got it. Carbides are chemical bonds formed between carbon and various alloys (or iron), which are very hard and contribute to wear resistance, also, in the annealed state, that's where most of the alloy and carbon is.
 
Larrin said:
Change your theories to fit the fact that the white spots are carbides, and you got it. Carbides are chemical bonds formed between carbon and various alloys (or iron), which are very hard and contribute to wear resistance, also, in the annealed state, that's where most of the alloy and carbon is.
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YEAH!:D Sweep the leg Johnny! :D :D thanks man
 
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