A ceramic is generally defined as any inorganic nonmetallic material.
Examples of such materials can be anything from NaCl (table salt) to
clay (a complex silicate). By this definition, ceramic materials would also include
glasses; however it is considered that the definition "ceramics" must also be crystalline.
The word ceramics comes from the Greek word keramos which means pottery.
Engineering ceramics are formed in the wet plastic state, dried and then
sintered at high temperatures. Monolithic engineering ceramics are derived
mainly from inorganic materials and often possess non-metallic properties.
Ceramics are closely associated with our everyday life.
Functional ceramics are distinguished from conventional ceramics (chinaware)
and called "fine ceramics" or "engineering ceramics."
Engineering Ceramics Include
- silicon carbide
- silicon nitride
- Cubic boron nitride
- Tungsten Carbide
Engineering ceramics are ideally suited for high performance
applications where a combination of properties such as wear resistance,
hardness, stiffness and corrosion resistance are important.
In addition to these properties, engineering ceramics have
relatively high mechanical strength at high temperatures.
Engineering ceramics are distinguished from metals and some alloys by their
exceptional properties. They are very hard materials and are highly wear-resistant.
Indeed, when compared to their metal counterparts, engineering ceramic parts and
components are more durable and have longer life-spans under given operational
conditions. Ceramic cutting tools, for instance, require less sharpening or replacement
due to wear, and will last at least 60 to 100 times longer than steel blades.
Engineering ceramics are chemically resistant to most acids, alkalis and
organic solvents and can withstand high temperatures. Metals weaken rapidly at
temperatures above 816oC while engineering ceramics retain a good degree of their mechanical properties at much
As most metals are approaching the limits of their capability,
engineering ceramics are emerging as the most desirable alternative for various
high performance high value applications. Frequently viewed as a direct replacement
material for top of the range metals such as tool steels, stellite and tungsten
carbides, the Ceramic materials produced are generally able to provide even better service
if they are engineered for the applications
Engineers have long considered engineering ceramics as hard and
brittle materials that are prone to catastrophic failure under tensile loading
conditions and are considered to be unreliable materials. However, technological developments over the last two decades have shown
that ceramic materials, are viable alternatives to metals and alloys in many
applications. As an example Zirconias have better wear-resistant properties than metals, are usually
corrosion-resistant, can withstand higher operating temperatures, possess a
thermal expansion coefficient close to many metals, and can be appropriately
bonded to metals.
Typical mechanical components include wear plates and thermal barriers, bearings for high
speed and high stiffness spindles, bushes, gears and many others.
Typical Process components include pump shafts, seats, bearing surfaces, gears
and even complete pump bodies, valve guides and seats.
Ceramics are used for cutting tools including razor blades for film and tape cutting to
300mm diameter circular slitters for the paper industry.
Ceramic turbine blades are used in most turbochargers providing lighter units than
the steel alternatives allowing improved performance at higher temperatures.