scratch resistance

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shaiko

Joined
Apr 20, 2013
Messages
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A question about blade scratch resistance...

If I have 2 mirror finished bladed both hardened to 58RC:

1. First is Made out of 440C
2. Second is Made out of S35VN
Will the plain 440C be more prone to scratches?
In other words:
Do the hard Vanadium Carbides in the metal matrix of the S35VN improve the scratch resistance of the blade?
 
Technically, yes. But that is not to say that any mirror polished blade will not scratch in use. I never mirror polish because it is a fool's chase.
My rule is:
"If a blade is soft enough to mirror polish, it won't resist scratching. - If it is hard enough to resist scratching, it won't mirror polish."

Make a good blade, HT it well, and leave a very smooth satin finish. I believe that the trend toward the "Brut de Forge" blades is because polishing is basically a waste of time, and hand sanding takes a lot of time.

The Japanese leave a lot of forging and finishing marks because the edge will cut if the blade is made right....... and the bulk of the blade does no cutting.
 
"If it is hard enough to resist scratching, it won't mirror polish" - it isn't true.
I once had a 85RC tungsten carbide preform polished to a mirror finish...it took 6 hours to do (for an object - the size of a bottle cap) but the result was a beautiful and flawless mirror surface.

I'm not saying it's wise to do on a full size steel blade - my question is theoretical. "Is wear resistance and scratch resistance are 100% synonyms"?
 
Last edited:
shaiko said:
I'm not saying it's wise to do on a full size steel blade - but my question was purely theoretical. "Is wear resistance and scratch resistance are 100% synonyms"?
Click to expand...

In terms of knife blades, perhaps 90% synonymous, because there are other factors involved... But basically, yeah. The sciency-type folks measure "wear-resistance" by literally scratching/abrading surfaces a set number of times with standardized materials, and measuring the weight difference before and after.
 
The reason I said "blade" is to avoid people talking about polishing tungsten carbide tooling and such. The knife steels you mentioned will always scratch at any usable hardness.

I was ( still am) a lapidary for years before becoming a jeweler, I have polished sapphire, and even diamonds. They can be taken to an optically flat surface and have amazing reflectivity....and won't scratch. But they are hundreds of times harder than any knife blade made.

A blade made from the steels we normally use will be exposed to dust and grit, as well as hard surfaces. These things are harder than the steel surface, and will abrade it , even if it is barely a .000000001" deep scratch. On a matte finish, this is invisible because the surface is composed of millions of larger scratches. On a mirror polish blade, the minute mark will show because it is all alone as well as the fact that it disrupts the reflection, thus creating an optical effect that greatly magnifies the mark.
 
shaiko said:
Do you know of any websites where I can get a difinitive answer to my question?
Click to expand...

You already have a definitive answer to your question. Yes, steels with vanadium/tungsten/molybdenum/chromium carbides resist scratching better than alloys without them.
 
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