amightydirge: WOOTZ-DAMASCUS STEEL: A BRIEF INTRODUCTIONwith sourcesWhat is Damascus steel? &a

amightydirge:

WOOTZ-DAMASCUS STEEL: A BRIEF INTRODUCTION

with sources

What is Damascus steel? 

“Damascus steel” is the name given to a type of steel historically produced in the Middle East and in India. It was first produced in India, sometime in 200 B.C. Initially referred to as “Wootz” steel, returning Crusaders named the steel blades after the ironworking center. Damascus blades were held in near-mythical regard, being sharper and more resilient than any blade produced in the West. A characteristic trait of Wootz-Damascus steel was its bands of light and dark metal, called “watering,” “firind” or ”jawhar.” A historical example of Wootz-Damascus steel:

Wootz and Damascus steel are the same materal. Both the Middle East and India produced ingots and forged them. The notion that India only produced ingots, which were then traded to the Middle East and then forged is nonsense. 

However, there is a difference between Wootz-Damascus steel and “faux-Damascus.” Faux-Damascus is simply pattern-welded (see below for an explanation) steel which maintains the characteristic light/dark bands of steel, but does not have the extraordinary material properties of true Wootz-Damascus steel. An example of modern, faux-Damascus:
Wootz-Damascus steel was lost in the middle east sometime in the 18th Century, but the practice hung on India into the 19th Century. The steel was produced until the destabilization and destruction caused by British colonization. 

How was Wootz-Damascus made? 

Forging steel is an incredibly complex process. Wootz-Damascus steel relies on several factors:

a) a proper crucible forge, and extremely fine temperature control

b) specific ores which contained choice impurities, like molybdenum, vanadium, tungsten, phosphorus and others. In the same way that carbon can be added to iron to make it stronger, other, smaller elements will increase the strength of steel further

and

c) a specific, lost technique of using natural materials like leaves and wood biomass to carburize the iron, adding carbon microstructures to the microscopic structure of the steel matrix.

Pattern-welding is often associated with Wootz-Damascus steel, but is not actually a part of the process. Pattern-welding is the practice of taking two different types of steel, placing them in alternating bars, then heating the bundle together and folding and twisting the metals together as they are hot-worked. This produces a spiral pattern reminiscent of Damascus steel. However, pattern-welded steel is inferior to both true Wootz-Damascus steel and 19th Century European homogeneous steel. 

Why was Damascus steel feared and respected?

Source 1 and Source 2 for the following:

Wootz-Damascus steel displayed a combination of hardness and flexibility which seemed impossible to ironworkers of the time. Iron, by itself, is very soft and does not hold an edge well. However, if carbon is added to iron during forging, the iron becomes denser and harder, creating steel. However, as you add more carbon, the steel becomes harder and harder until it is so brittle it will simply break when struck upon something. 

These two properties are inversely proportional, so in normal steel working you must settle on a mix of hardness and ductility that best suits your needs. 

However, Wootz-Damascus steel is both superplastic and extremely hard. The structure of Wootz-Damascus steel contains two types of steel - a soft steel called ferrite and an extremely hard steel called cementite (Fe3C). Steel can actually be many different allotropes of steel, all of which are differentiated by their internal micro-structure. Consulting a phase diagram for iron and carbon: 

The left axis is temperature, and the bottom axis is carbon content. As you increase temperature, or increase carbon content, the types of allotropes produced varies. All Wootz-Damascus examined so far is hyper-eutectoid, that is, it contains from about 1% to 2% carbon content. This is an extremely high carbon content, and would be useless for weapons if produced by European blacksmiths. They had no way of tempering the extreme brittleness of cementite. All European weapons were in or near the hypo-eutectoid range (less than .83% carbon content). 

The secret to Wootz-Damascus steel lies both in its ore and in its carburization process.

Judging from the composition of historical Wootz-Damascus steel blades, the ore used by Middle Eastern and Indian metalsmiths contained trace amounts of other elements, such as molybdenum, vanadium, and tungsten. In modern times, such elements are used in steel production to produce stronger steels. Adding impurities into iron works because iron atoms are so large there is “room” for smaller atoms to be shoved into the crystalline structure: 

The above image is for carbon atoms, however, elements like vanadium and tungsten are smaller than carbon atoms, so can be fitted into the crystalline structure even in the presence of carbon, filling in whatever else is left. Testing has shown that vanadium traces as low as 40 parts per million are enough to significantly alter the structure of the steel as a whole, creating cementite bands and cords. By having the cementite allotropes cluster together in bands, it helps to strengthen the material, also aiding in creating the characteristic waves and patterns. 

By far the most significant process used was that of carburization. In usual terms, carburization is a hardening technique which heats metal in the presence of some carbon rich material, the carbon is then found on the surface of the metal, hardening it. Wootz-Damascus carburization produced an entirely different result, however. 

Wootz-Damascus steel contains carbon nanotubes, a material that was only recently invented in the last two decades. Carbon nanotubes are a special type of carbon allotrope where carbon atoms bond in a peculiar tube formation, with a dominating hexagonal pattern:

Carbon nanotubes have a wide variety of strange and extraordinary properties, but the properties most significant to the production of Wootz-Damascus are its hardness, elastic, and strength. 

Carbon nanotubes are the strongest materials currently known to man, both in terms of tensile strength and elasticity. This means they can bend and flex without breaking easily. However, they are also extremely hard, the bulk modulus of carbon nanotubes exceeds that of even diamonds (460+ GPa for carbon nanotubes vs. 420 GPa for a diamond). This means that carbon nanotubes display an unprecedented combination of both strength and flexibility, which is something that pure steel cannot even come close to replicating. 

Nanotubes observed in a 17th Century Middle Eastern Sabre are found to encompass the cementite cords - the allotrope of steel which is usually too fragile to be used in weapons. The carbon nanotubes act as a sheath, reinforcing the cementite cords, allowing it to be both strong and malleable. The mythic properties of Wootz-Damascus steel are derived from this extraordinary and amazing steel structure. 

It must be noted that modern carbon nanotubes are produced using expensive and advanced methods, such as using high amperage arcs of electricity, plasma torches, or pulsed lasers. Somehow, ancient metalworkers were able to produce carbon nanotubes using a specific blend of ores, woody biomass, and leaves, treated and forged in an process unfortunately lost to modern engineers.