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So let's say that I have a tool that's made of a very tough and hard material, like tungsten carbide or some kind of gem stone.

My understanding is, there are limits to every material, that up until that limit the material will not crack. Also, my understanding is that the mechanisms of wear on a material is mostly adhesion, another material that has enough force to dislodge particles of a material, eroding and wearing it away.

So I was wondering, if you had a very hard material that was only subjected to very small forces at a time, like rubbing against some metal with very light force, would this eventually wear away the harder material, no matter how minor the force, or is it possible to maintain a level of force that is so small that there would never be enough force to dislodge any particles and introduce any fatigue in the material?

Also, out of science-fiction curiosity, could there be some kind of nano-technology that would be able to reinforce the molecular bonds in a material, making it self-healing and actively applying force between the bonds to keep the material together through friction? How would something like that work?

Thanks

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is it possible to maintain a level of force that is so small that there would never be enough force to dislodge any particles

This is SUCH a good question! Answer: yes, and no.

Hard materials, by normal material-properties analysis, are not susceptible to attack with small forces (below the stress that would fracture a hard material there is expected to be no loss of integrity).

What REALLY happens, is more complicated.

First exception: A polishing compound is too soft to abrade steel, but if you apply it, the compound comes away black, loaded with iron-containing oxides. That is because steel has an oxide layer, sometimes transparent, which is softer than the metal. The polish contains abrasive particles which fracture before they scratch the metal, but which might abrade the softer oxide.

Chemical degradation of the steel surface (oxidation) will proceed after the top layer is polished away, at the fresh exposed surface. The combination of physical stress and chemical (oxidation) attack does 'wear' the hard material.

Second exception: a steel wire, under tension, can slowly (over months) stretch even at low force. This is called 'creep'. Temperature determines the hardness of a material; local parts of the material may be at almost ANY temperature (there are random local fluctuations, because thermal motions are necessarily random). With continued force, a slow flow occurs, even if the nominal yield strength does not allow it. Creep in steel is also associated with nitrogen content (a few atoms of nitrogen can destabilize the strength of strained regions), so music wire (piano wire) is made of low-nitrogen steel.

Third exception: no material is completely pure, and even if it were, cosmic rays or radioactive decay can penetrate and leave damage. Dating of some crystalline minerals, and fired ceramics, is done by noting these damage tracks. That means that the material hardness, while accurate for large samples, is variable internally.

So, a hard material can be attacked chemically, or can recrystallize under stress, or can stop a cosmic ray and take damage in the absence of ANY applied force. A variety of external circumstances other than simple application of force is unavoidable.

could there be some kind of nano-technology that would be able to reinforce the molecular bonds in a material, making it self-healing and actively applying force between the bonds to keep the material together

Sure. Broken bones heal. A kind of wood finish, rubbed oil, can 'heal' after taking a dent. Galvanized iron maintains a zinc layer by a kind of electrochemical healing. Halogen lamp filaments chemically deposit fresh metal over any hot spots (which makes them more durable).

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  • $\begingroup$ Interesting, I had a rocking chair that I kept poking with a toothpick, and darn if that thing didn't heal itself from the damage. I had to poke it many times before it stopped healing, and then the healing was partial. $\endgroup$ Commented Dec 19, 2023 at 14:22
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Some years ago I was confronted with a situation where a soft-metal bearing was apparently wearing away a hardened steel shaft. After much head-scratching (and microscope work) it appeared that the soft metal had been embedded with work-hardened microscopic debris from elsewhere in the machine, transported there by the lube oil, and small enough to pass though the oil filter.

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