Does Damascus Steel Outperform Super Steels?

[Ian]

Larrin Thomas at Knife Steel Nerds has just completed a lengthy piece on "Does Damascus Outperform Super Steels? Testing Different Combinations."

For anyone unfamiliar with Knife Steel Nerds, this is a great site to learn about the technical aspects of metallurgy and steel. Larrin has his own laboratory and approaches steel as a scientist. He has written several books on the subject. I've also found him very approachable and friendly, willing to share his extensive knowledge.

His latest discussion on "Damascus" (i.e., pattern pattern-welded steel) is very interesting, and he examines several claims about pattern-welded steel and its ability to cut well. I think you will find his conclusions interesting. The micrographs of Damascus steel are stunning and the research is backed up by his usual excellent charts.

There is also a video of the topic on the Knife Steel Nerd site.

[mariusgmioc]

... but not surprising at all.

Pretty much everything he said was well known or intuitively deductible for anybody familiar with steels and their properties.
However, his main "surprise" conclusion is about "damascus cutting properties" which I believe to be completely irrelevant.

He concludes that pattern welded damascus cuts better because of a serrations effect between hard and soft layers.

However, it is unclear what this "cuts better" means as cutting properties depend hugely of the geometry and microgeometry of the edge not of the material of the knife (mostly as there are some subtle nuances even here). So this whole "cutting well" discussion is an upstart fallacy, and I have suspicions that his testing method does not respect all the rigors necessary to reach a valid conclusion. More specifically, there are way too many parameters to take into account to be able to draw a correct conclusion and the omission of one single parameter, no matter how insignificant it may be, can lead to fundamentally different results.

For example, the cutting properties depend significantly (among others) of the angle by which the edge was sharpened and the grit of the sharpening stone. If the sharpening was done along the edge line, the cutting effect may be worse than if the sharpening was done perpendicular to the edge. If the sharpening is done perpendicular to the edge the grit of the sharpening stone creates micro-serrations in the edge that help its cutting properties. However, each material is cut better with a specific size of these micro-serrations, micro-serration that at their turn are dependent on the grit of sharpening stone. So the micro-serrations that cut meat better might be worse at cutting potatoes.

Moreover, while modern mono-steels can guarantee a good level of consistency in conducting cutting tests, pattern-welded damascus is much less consistent, as it is practically almost impossible to predict the micro-geometry at the very cutting edge that will result after sharpening, because of the heterogenous nature of pattern-welded damascus. So, if you have three billets of the same pattern-welded damascus and you sharpen them exactly the same way, you may end up with three blades with three different cutting properties, resulted from three different edge micro-geometries that in their turn are the result of the heterogeneous structure of the pattern-welded damascus.

[Ian]

marius,

I think you are being a bit hard on Larrin. What he set out to do, in part, was to examine some of the long held beliefs ("myths") about pattern welded steel for which there has not been firm scientific evidence. While his findings may confirm some previously held beliefs/convictions, his work shows that some of those beliefs have some factual basis and are not just wishful thinking or traditionally held beliefs (myths).

As far as standardizing his methods, Dr Larrin Thomas is a professional in his field of metallurgy, and well known (at least in the U.S.) for his strong scientific methodology. If you read his web site, you will find a lot of the experimental work he has done on many, many different steels.

His recent work on Damascus (pattern-welded) steels produced a number of important observations IMHO. For example, if you take two carbon steels of different hardness (one hard and one soft), and pattern weld them, you end up with a steel of medium hardness because the carbon "flows" readily and equalizes its concentration across both steels. That's an interesting observation that I had never heard before and may be a new scientific finding.

Another observation that I found fascinating was the effect of pattern welding pure nickel with a hard steel. The nickel is soft, and reduces the overall hardness of the blade, but it led to much improved cutting properties! This related to the alternating pattern of hard steel and soft nickel along the blade's edge, producing tiny serrations as shown by his excellent photo-micrographs.

While one could say these observations are intuitively obvious (they were not for me), the demonstration of these features in a scientific manner is what sets Larrin's work apart from guess work or "experience."

[A. G. Maisey]

I thought Larrin's investigations to be pretty interesting, perhaps nothing unexpected, but really useful to see it all laid out so clearly.

In respect of better cutting ability of damascus if compared to non-damascus blades.

In another lifetime I made a lot of blades, both damascus & non-damascus.

I made simple blades, the materials I used were 01, motor vehicle spring steel, nickel, mild steel, wrought iron.

I made mostly random pattern damascus and I heat treated in the forge, not by sending my blades to a heat-treating company.

As I said:- simple blades.

Cutting tests that I carried out using manilla rope invariably demonstrated that damascus 01 + nickel cut more manilla rope than damascus 01 without nickel, & both cut more manilla rope than 01 & spring steel.

This is purely a comment on my own experience in making, using & selling blades I made myself, I am not up for debate on any aspect of this.

EDIT

It has been pointed out to me that I have only told a part of the story.

The cutting/slicing ability of a blade depends in large part on the heat treatment, yes, blade geometry is important, but it is the heat-treat that provides a long lasting ability to cut --- or not.

In the case of a blade made with non-laminated steel, ie, non-damascus, it is essential to draw the temper to protect against gapping & fragility.

In the case of a laminated blade, it is not necessary to draw a blade if its intended use is to cut/slice, rather than to chop.

If that laminated blade is not drawn it retains the full hardness that was achieved in the quench, thus the cutting ability is retained for longer.