Dull-Re-SiO2

BluntCut MetalWorks

BluntCut MetalWorks

Knifemaker / Craftsman / Service Provider
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Apr 28, 2012
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Do-re-mi my edge is getting duller by SiO2. Would you agree SiO2 is the predominant actor/factor in wearing/dulling edges? Let's define edge dull from wear, not from fracture/chip; roll or other deformations.

https://en.wikipedia.org/wiki/Silicon_dioxide

SiO2/quartz hardness around 820 knoop ~ 64rc. SiO2 will wear away steel matrix in pressure+draw/saw+impact cuttings. Carbides (even cementite) will provide some matrix shielding from SiO2. Shielding is proportional to sawing component of the cut. i.e. pure pressure/push cutting = zero saw/length-wise component. That's right, your s110 or 10v edge will dull after a few cut of materials heavily loaded SiO2.

IMO, a stable 64+rc matrix is a big key for attaining higher overall edge retention. Well or at least it's my rationale for chasing 64+rc matrix in the last 3+yrs tinkered with ht.

Your thoughts?
 
I agree. SiO2 (silicon dioxide, a.k.a. 'silica') is essentially 'sand' (or 'dirt', or 'glass') in how I view it, and none of those have ever been good to my edges, no matter how wear-resistant a steel is supposed to be. Silica always rears it's ugly head in cutting fiberglass or anything 'dirty' with it. I live in the constantly-dusty desert southwest, with airborne sand/dust all the time, so I'm frequently reminded of it's dulling effects on cutting edges as well as scratching stuff, like car finishes, eyeglass lenses, etc.


David
 
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:thumbup:

With reasonable certainty, a blade with stable matrix hardness 64+rc would reduce wear from SiO2. Sure, this is to be seen/prove :p

Obsessed with Edges said:
I agree. SiO2 (silicon dioxide, a.k.a. 'silica') is essentially 'sand' (or 'dirt', or 'glass') in how I view it, and none of those have ever been good to my edges, no matter how wear-resistant a steel is supposed to be. Silica always rears it's ugly head in cutting fiberglass or anything 'dirty' with it. I live in the constantly-dusty desert southwest, with airborne sand/dust all the time, so I'm frequently reminded of it's dulling effects on cutting edges as well as scratching stuff, like car finishes, eyeglass lenses, etc.


David
Click to expand...
 
So the question being raised is how would one measure the effects of SiO2 on comparable alloys and edge geometries while limiting the variable to being the hrc?

Loosen the wraps of a 10' length of 3/4" manilla rope and roll it in some sandy/dusty/loamy dirt and cut that with "X" amount of cuts and observe edge wear vs a control (clean) rope?

If you have a noticeable drop in edge wear/damage vs (perceived) effort or a significant amount of cuts prior to edge failure (25, 50, 100+) would that be enough to push further inquiry or satiate your curiosity, albeit temporarily?
 
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Just a simple man checking in. I know that some woods have so much silica that tungsten carbide tipped blade are recommended when processing. My dad has worked with teak that will trash regular saw blades. I have whittled scraps and it is like cutting a piece of cement.
Luong, whatever you are up to, I am all eyes and ears. I know your high hardness steels hold an edge really well, even when you aren't happy with them.
Carry on, this could get good.
Russ
 
Thanks, Russ/mycough!

I think, it could be simple to check/test.

Wear glove. Dip 3 pieces of stiff cloth into thick CA (cyano-acrylate) -> twirl in sand pile to adhere it full of mostly fine and super fine sand

Sand diamond (alright, maybe substitude with mirror polished coarse tungsten carbide block)

Sand highly mirror polished s110v or 10v 60rc blade

Sand 68rc low(close to zero) alloy simple carbon mirror polished blade

Do 300 sand strokes each for each surface. If neccessary - repeat this experiment a few times to avg out inconsistencies in sands & strokes.

Well, if SiO2 rc is 64rc or less, which surface - you think - suffer higher scratches?
 
If the stable high rc matrix is the crux of the biscuit so to speak then the 10v is going to be worse for wear.
I seem to remember a pretty crafty guy using a sand box as a test media in the past... or perhaps I am mistaken and the Sands of time have clouded my memory... I think it may be time for bed, carry on gentlemen.
Russ
 
Russ & Chris - decades from now, your mind won't able to recall old stuff like this sand box to haunt me, eh!

Cutting through sand is more a test of macro wear (abrasive 100-1500um) and impact toughness on thin cross section (namely apex). A modify cutting medium could be use to simulate high wear rate from sub micron silicate/SiO2 <= could use hand centrifuge to collect sub micron silicates. oooohhh nooo bad guys could this trick to refine something more deadly, so I won't disclose exactly how arm twirling water in a bucket full of sandy water and centrifugal force magic works. OK, mix a kg of this fine silicate with wet-clay (or something similar but even less abrasive).

Or go to a slough with 2 blades (high & low rc matrix) side by side - slice them through soft muddy stuff for 5m or so. Take picture + slice test. Repeat a few times. Post result.

I am looking forward to seeing result from at least a few of you - sharpening & knife knuts.... I want this result yesterday, so get to it now :D

Oh heck for my part, this afternoon. I used wine cork to rub sandy dust against my 66.5rc W2 blade and old experiment 62rc D2 blade. Polished that D2 nifty well. W2 blade got brighter but there weren't much length-wise (rub direction) scratches to erase vertical grinding belt scratches.
 
Silica is what most natural sharpening stones are composed of - it's their main abrasive component. Arkansas stones are nearly 100% silica, and most other natural sharpening stones are at least 60% silica... So yes, it is certainly abrasive. That's not really a revelation, lol. It is a very common substance - even floating through the air as dust.
 
Wouldn't it good to find out whether having a matrix harder than SiO2, improve edge retention by reduce wear rate? I think, yes but that need to be proven by others...

eKretz said:
Silica is what most natural sharpening stones are composed of - it's their main abrasive component. Arkansas stones are nearly 100% silica, and most other natural sharpening stones are at least 60% silica... So yes, it is certainly abrasive. That's not really a revelation, lol. It is a very common substance - even floating through the air as dust.
Click to expand...
 
If the matrix is harder than SiO2, theoretically the abrasion resistance needed will jump up several levels. A knife like that will be able to whittle bamboo without much edge degradation.

Now, I imagine this matrix like a cube, with the molecules arranged around this format. Are carbides (T, W, Cr, etc) still useful? If yes, how many and where' it should be placed?
I don't have enough background on metallurgy, but it's getting interesting. A tightly packed SiO2 at submicron size will get to the matria beyond what carbides can protect, I think.
 
Moose and bear hides are usually very gritty (SiO2) and will dull a blade very quickly if you try to saw through the fur instead of cutting "inside out" (i.e., make a slit, then slice the hide edge up). I doubt there is any steel that will stand up against that stuff.
 
Better late - corroboration - than never :)

Fe(CPM M4) and Fe+Co(CPM T-15) composite matrix vs silicate abrasion

YogPrJH.png


https://www.bladeforums.com/threads...ving-foundation.1409721/page-44#post-19410304
 
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