wear resistance vs toughness

D

dogknott

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Sep 10, 2009
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Whats the difference?

Read where D2 is highly wear resistant but not very tuff. That didn't make much sense to me, so could someone explain it to me please.
 
Wherre are the general informations about steels grades, steel properties, blades and edges?

Wear resistance inidicates, if it will take longer to dull the edge compared to another steel grade.

Toughness inidcates, if it will take more force to break the blade.
 
Sorry, no answer from me, but I like the question and I'll be very interested in the answers given. I have puzzled over this as well.
 
Wear resistance means that it will take longer for the blade to dull. The harder a material is, the more wear resistant but also the more brittle. For example, a diamond is the hardest material we know of, so it would be extremely wear resistant but not very tough because you could smash it apart with a hammer or rock.

Toughness means that the blade can bend and absorb more shock without breaking or chipping. A prybar would be an example of something that is very tough as it can be used to pry doors from houses and cars without breaking, but the trade off is that it would be made of a relatively soft steel and if sharpened would not be able to hold an edge for very long at all.
 
Thanks!!, now doe's Rockwell hardess come in to play as a combination of hardness/ware resistance?
 
The Rockwell scale is just a way to measure the hardness of a given steel. The harder a steel is, the more wear resistant.
 
ieraseu said:
Wear resistance means that it will take longer for the blade to dull. The harder a material is, the more wear resistant but also the more brittle. For example, a diamond is the hardest material we know of, so it would be extremely wear resistant but not very tough because you could smash it apart with a hammer or rock.

Toughness means that the blade can bend and absorb more shock without breaking or chipping. A prybar would be an example of something that is very tough as it can be used to pry doors from houses and cars without breaking, but the trade off is that it would be made of a relatively soft steel and if sharpened would not be able to hold an edge for very long at all.
Click to expand...

this has always been my understanding. well put
 
There are basically three ways to dull an edge: rolling, chipping, and abrading. Different properties of the steel determine a blade's resistance to each of these factors.

A harder blade will resist rolling, but with reduced toughness that may result in chipping. Abrasion resistance is highly dependent on the alloy itself, and less dependent on hardness. Many steel companies will have charts showing how these factors relate to hardness in a specific alloy.
 
And where does flexibility stands in?
Is it domain of alloy, or rather optimal heat treatment?
Because in most cases "tough" knives bend, and "hard" knives break. How can we make it flex?
 
This is good info!!

The reason i ask is, i'm looking for knives that stay sharp when skinning critters, have a Queen D2 now that i'm going to try, have a CSC 14-4CrMo on order. I can keep any knife razory till i get to the head area of a critter, then it goes dull. Useally just tune up the edge in the feild, but would rather not. Have used Shrade 77OT's and Uttica Kutmaster's in the past,great knives, just tend to dull quick.
 
Flex is dependent on geometry, nothing to do with hardness/toughness. A dead soft and as-quenched bar of the same steel will flex the exact same amount. Flex is the movement of the material within the elastic range, where it springs back to true when the load is removed.

Once you get past the elastic range, then you enter bend or break territory. A stronger (harder) steel will require more force to permanently deform it, while a softer steel will bend at a lower force, but also range a bit further from this plastic deformation to catastrophic failure.

Wear resistance is also influenced by alloying content and subsequent carbide makeup within the steel. It is not so easily tied to toughness and strength.

ETA: a good way to think about toughness and strength is to just look at how they are measured. Strength correlates to hardness, which is measured by the amount the steel deforms/dents when a load is applied through a diamond point. Toughness is measured with izod/charpy type tests. With these tests, the steel is hit with a hammer. Strength-stress deformation resistance. Toughness-impact fracture resistance.
 
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IMO ideally it will have some flex, the edge will roll instead of chip while still having great edge holding ability and still being tough enough, around 58-60.
 
There are conflicting examples of the uses of these words all over the industry. Generally wear resistance is what the words mean. If a blade has high wear resistance it won't dull quickly. Toughness usually relates to the steel's ability to resist lateral pressure without deforming and without breaking. So if you were to wedge a blade then pry with it, a tougher blade would withstand more pressure than one that is less tough.

Hardness is one factor. Harder blades will, by definition, resist wear better than blades made from the same material that are softer. But it is more complex than that. Some steels (tool steels are a good example) have alloying elements that allow them to be more resistant to wear than other steels treated to the same hardness. Carbides, as an example, are very wear resistant so blades with more carbides will be more wear resistant than others.

Softer steels are usually tougher. The reason is that they are less brittle so they will take more prying force than harder blades made from the same material. But that isn't the whole answer there either. Some alloys will be tougher even though they are more brittle. Others will be more or less brittle than alloys hardened to the same degree.

The two measures are somewhat mutually exclusive. By that I mean that wear resistant blades are usually less tough and vice versa. But some alloys have become famous for having a very good ability to do both. VG-10 is a good example of a stainless steel with good edge retention and yet plenty of toughness to handle jobs that call for it. You can find better examples of either wear resistance or toughness in other steels but there aren't many stainless steels with a better combination of the two. Because it has good compromises in both directions, it is a successful knife blade material.


So, if you think of wear resistance as a measure of edge retention and toughness as a measure of the ability to take prying pressure, you won't be too far off the mark. Just understand that the reasons behind them might be less than obvious.
 
ieraseu said:
The Rockwell scale is just a way to measure the hardness of a given steel. The harder a steel is, the more wear resistant.
Click to expand...

And conversely, the higher hardness, the more brittle, which is less toughness.
 
J_Curd said:
And conversely, the higher hardness, the more brittle, which is less toughness.
Click to expand...

Generally yes, A2 on the other hand has better toughness at 60HRC than 56-57...
Probably there are other weirdos like that.
 
Yeah, we need Larrin...that guy makes complex steel discussions simple enough even I understand it all :D
 
Thanks for the clarification, what you said makes sense now. A stringently defined "flexibility" made it all come together :)
 
Wear resistance is the ability to resist abrasive wear. Very wear resistant steels will have less material removed when held to a grinder or used to cut abrasive material, like used carpet from a beach house.

Toughness is generally defined a couple of ways. First is impact resistance. This is the ability to withstand sudden impact without breaking. Glass has a very low impact toughness. Chopping knives and axes need high impact resistance.

The other way to define toughness is the ability to resist breaking when flaws are present. Smooth glass has pretty high strength, as long as there are no flaws in it. If you score the surface with a glass cutter, then you can literally break it with your (cut protected) hands. I've seen welder's test pieces fail because there were large flaws in the weld. Cracks start at the flaws and then run through the material. Rope has very high breaking toughness (or fracture toughness) because there can be broken threads (flaws) and the remaining threads are unaffected. Imagine having a large machete with a very coarse finish, say it was finished with a 24 grit belt. All those scatches are essentially very shallow cracks and a crack will eventually start at one of them and run through the blade, breaking it.
 
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