How well does damascus perform?

[Alpha Knife Supply]

The making of pattern-welded blades promptly fell out of use as the homogeneous steel blades took over the market. That should tell us something about the comparative qualities of homogeneous versus pattern-welded steel.

Please clarify this statement in detail.

 

[Kevin R. Cashen]

People seem to hold it in very high regards, but I can't ever seem to afford it to test it out for myself.

I can’t really afford it either, but I am fortunate enough to have the stuff laying all around my shop, so I have tested it at every opportunity. When I say test I don’t mean whittling on something for a minute and proclaiming one virtue or another based on my likes, I mean meaningful material testing.

What has been said previously in the thread is true, pattern welded material is a process more than a product and an endless variety of materials can result from it, ranging from excellent to very poor. It is all dependant upon the materials used, techniques employed, skills of the maker, final heat treatment etc… With all the variables possible I am confident in saying that you chances of getting a stinker with pattern welding are greater that the safer route of carbon steel. So know the maker and “caveat emptor”.

As for what Damascus is – it is a town in Syria, and that is all one can say definitively. Ancient crucible steels were not called in their time by that name either. Pattern welding was not called damascus in ancient times as well. Damascene effects in a variety of material have been around for some time, brocaded cloth is called damask, and many inlayed metal treatments are known as damascened. It all seems to stem from 18th or 19th century terminology to describe patterning, so I think we must be willing to accept that it can apply to any patterned steel, or admit that it is a complete misnomer for welded or cast steel. I was very interested in Ann Feuerbach’s lecture at the Ashokan seminar in Sept., she spent a bit of time on the terminology and ancient language names for what we now call “wootz”, which is an incorrect corruption of an original word, so it would appear the not only is the title “damascus” erroneous but the word “wootz” is a fairly modern invention as well. It would appear that language evolves and we need to be flexible or all proper terminology will simply fade into antiquity.

The abandonment of pattern welding in with the advent of larger blooms and better hearths is not an indication as to the quality of the original materials but a result of the need for efficiency. One needs to examine why they were welding up blades to begin with. Technology had not reached the point at which homogeneous material could be produced in satisfactory amounts for entire blades. When that technology came about, and one had to supply and entire army with metal weapons, it was just impractical to take the time to weld up all those pieces. Handmade furniture being mostly replaced with assembly line stuff says absolutely nothing about the relative quality of either, it just makes more sense if you need to make a lot of chairs, and some would argue that the handmade chairs are better.

My study shows that if one combines good materials of differing abrasion resistance, a pattern welded blade will cut more aggressively on certain materials due to a micro-serration effect. I have seen some pooh-pooh the very notion of this, but to them all I can say is “show me your micrographs, and I’ll show you mine”.

If the material is made right (a big if these days), my studies have also shown that the weakest link hypothesis does not necessarily win out, I find a compromise. Lets take my pet mix of O1 and L6, some would say that L6 would lose its toughness to the O1 and the O1 would lose its edge holding to the L6, that the blade would only hold and edge as good as L6 and only take a shock as good as O1. I find that the shock resistance is a little less than straight L6 but a little higher than O1 and the same with edge holding. So one could just as easily say that the O1 has gained toughness and the L6 has gained edge holding, and this is supplemented with a micro-serration effect in softer fibrous targets.

It is a very complicated topic and a very complex material that one simply cannot make any blanket statements about.

 

[RogerP]

Thank you for that most informative post Kevin. Regarding the following:

My study shows that if one combines good materials of differing abrasion resistance, a pattern welded blade will cut more aggressively on certain materials due to a micro-serration effect.

Which types of materials do you find are cut more aggressively by a pattern-welded blade?

Roger

 

[nozh2002]

I apologize for taking so long to get back to you. I think that Japanese swords, which are called "folded steel" in translation, are made much the same way as pattern welded blades from what I understand. But I am not a student of Japanese blades and the study of them is such a particular one that I am not prepared to venture much further than that. Perhaps one of the people who really understand Japanese blades can answer you better.

As I understand there were no different steels in old times. Now you can buy different types of steel and weld them toghether. But I doubt that bladsmithes 150 years ago had such a choise. Kuznetzov idea that damascus pattern is result of surface carbonization of same steel layers sounds reasonable. This way Japanese making katanas also, from what I know.

Thanks, Vassili.

 

[Kevin R. Cashen]

Which types of materials do you find are cut more aggressively by a pattern-welded blade?

Roger

I have found that the "damascus cutting effect" is accentuated by softer fibrous and slightly abrasive materials, like rope and paper and perhaps animal flesh covered by course hides with some grit. It works a lot like specialized abrasive wheels, very aggresive cutting ones wear down quicker, slower cutting wheels last longer. Metals with low hardening folded in will make a very aggresive rope cutter or paper slicer but will fade fairly fast on wood, hard cardboard or bone. Metals of comparible hardness and varying abrasion resitance will not be as agressive but will cut longer.

 

[Cliff Stamp]

My study shows that if one combines good materials of differing abrasion resistance, a pattern welded blade will cut more aggressively on certain materials due to a micro-serration effect.

What is the blade finish? I personally see little reason to support this for a number of reasons, mainly because I have looked at it with dendretic steels which are supposed to have the same effect and seen nothing, regardless of what the micrographs of the steel show, there is no induction of aggression.

Of course even homogenous steels like D2 are not actually truely homogenous. That steel after hardening will be a mix of tempered martensite, untempered martensite, pearlite, bainite, with all of these being various mixes of ferrite and cementite and other carbides in various aggregates. Thus there is a huge difference in local wear resistance, and the same holds for any steel of varying degrees.

As well, even the most contrasting steel, with large aggregates or highly contrasting mixes isn't going to have the aggression due to a coarse finish which can produce teeth so large you can see them by eye and thus is contrasting on the order of a 1000 microns. So for example a pure O1 blade with a x-corase finish should easily outslice a patten blade at a high finish.

Now you could maybe argue that the aggression in the pattern blade is more durable due to it being inherent in the matrix and thus stable with wear unlike the coarse tooth finish on the homogenous steel, and I can see a basis for that, I have proposed that idea myself and I have seen it happen with steels with high aggregates like D2, but the actual function benefit of this is low for a number of reasons.

I have seen some pooh-pooh the very notion of this, but to them all I can say is “show me your micrographs, and I’ll show you mine”.

I would find it hard to argue that point from micrographs of the steel, I would want to see the results of actual cutting done with the blades over a variety of finishes. The micrographs can be used to support the hypothesis that they are the underlying reason but this would need to be evaluated carefully as alone they don't indicate a direct correlation.

If the material is made right (a big if these days), my studies have also shown that the weakest link hypothesis does not necessarily win out, I find a compromise. Lets take my pet mix of O1 and L6, some would say that L6 would lose its toughness to the O1 and the O1 would lose its edge holding to the L6, that the blade would only hold and edge as good as L6 and only take a shock as good as O1.

Yes, that is readily wrong, by an extension of the same arguement a steel would have the toughness of the carbides and the wear resistance of the ferrite matrix. Proof by contradiction is one of the easiest methods of invalidating a lot of arguements. You will get enhancements of the weak points and essentially an averaging of properties of sorts.

-Cliff