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Composite Ceramics

Advanced ceramic materials have such interesting properties

that mechanical engineers are becoming more and more interested

in their use as structural parts (конструкционные детали).

Ceramic cutting tools have been in use for some time. However,

it is only during the last twenty years that there has been rapid

development in this field because of the development of new composite

ceramics.

Composite materials are materials in which two or more different

substances, such as metals, ceramics, glasses, or polymers are

combined without chemical reaction. As a result one can produce a

material with properties different from those of any of the individual

constituents. The constituents of a composite would retain their

individual characteristics.

Recently engineers have developed various kinds of composite

ceramics which must combine an increased toughness (пластичность)

with the same hardness and strength of usual ceramics. A

promising recent development is the addition of a tiny quantity of

metal to increase toughness and tool life. Thus, at room and high

temperatures (1000 °C) the composite ceramics for cutting tools

should possess the following properties: high strength, high toughness,

high hardness, high thermal shock resistance and high chemical

inertness.

Text 6C

Ancient Steel-Making Secret

When two metallurgists at Stanford University were trying to

produce a «superplastic» metal they became interested in the secret

of Damascus steel, the legendary material used by numerous warriors

(воины) of the past, including Crusaders (крестоносцы). Its

formula had been lost for generations.

Analyses of a new steel revealed properties almost identical to

those they found in Damascus steel, although their own plastic

steel had been produced by present-day methods.

The remarkable characteristics of Damascus steel became

known to Europe when the Crusaders reached the Middle East in

the Uth century. They discovered that swords (меч) of the metal

could split (рассечь) a feather (перо) in air and at the same time

retain their edge sharp through many battles.

The secrets of Damascus steel were known in many parts of the

ancient world, especially in Persia, where some of the finest specimens

were produced. For eight centuries the Arab sword makers

kept the secret about their techniques and methods. And with the

invention of firearms (огнестрельное оружие), the secret was lost

and it was never fully rediscovered.

The two metallurgists carried out a lot of researches. When they

realized that they might be close to the discovery of a new material,

a sword fancier (знаток), at one of their demonstrations, pointed

out that Damascus steel, like their own product, was very rich in

carbon. This led them to conduct a comparative analysis of their

steel and those of the ancient weapons. As a result, it was found

that a basic requirement was a high carbon content. The two metallurgists

believed it had to be from 1 per cent to 2 per cent, compared

to only a part of 1 per cent in ordinary steel. Their research showed

how to make steel of even greater hardness than Damascus steel.

Text 6D

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