Advanced Ceramics Products


Reaction bonded silicon carbide pump impeller

Advanced Ceramic Materials

Advanced ceramic materials are used increasingly to combat aggressive wear and corrosion within minerals handling and processing environments. Often referred to as exotic materials, advanced ceramics have not generally been considered viable materials by plant engineers for mineral handling applications. However, plant and design engineers are beginning to realise that the higher quality fine grained advanced ceramics substantially reduce maintenance and down time costs.

250mm Diameter Reaction Bonded Silicon Carbide Pump Impeller

The main reasons why advanced ceramics are becoming more generally accepted by minerals handling engineers are:

  • Better quality technical information and proven applications experience is more readily available.
  • Plant and design engineers are realising that ceramics materials are capable of dramatically outperforming traditional metallic materials in particularly aggressive applications and they are more appreciative of the cost/performance ratios of the materials they are selecting.
  • Managers are increasingly less willing to accept items of plant and equipment being replaced every few weeks or months because of abrasive or corrosive wear.
  • If advanced ceramics are properly selected and applied they will give excellent performance. It is important for engineers to realise that there is a wide range of ceramic materials available with vastly differing mechanical, thermal and chemical properties.
Reaction bonded silicon carbide valve ball
200mm Diameter Reaction Bonded Silicon Carbide Valve Ball
Reaction bonded silicon carbide spray nozzle

Spray Nozzles

Reaction bonded Silicon Carbide is used to manufacture abrasion and corrosion resistant spray nozzles operating at temperatures of around 1000 degrees C.

These spray nozzles were originally manufactured from inconel 600 and wore out within 2 weeks. They are now manufactured from reaction bonded silicon carbide. Wear and corrosion is now not a problem that is associated with these nozzles.

32mm bore Reaction Bonded Silicon Carbide Spray Nozzle

Lime Turbine Wear Chamber

Reaction bonded silicon carbide lime turbine wear chamber which rotates at 6000 rpm, or more, and operates at temperatures of around 150 degrees Centigrade.

The wear chambers were originally manufactured from stainless steel, which wore out within 2 weeks. They are now manufactured from reaction bonded silicon carbide and there is no wear or corrosion visible after 2 years of operation.

Reaction bonded silicon carbide lined lime turbine atomising
        disc
430mm O.D. Reaction Bonded Silicon Carbide Lined Lime Turbine Atomising Disc
Reaction bonded silicon carbide fluidised bed reactor bend

Pnuematic Conveying Pipe Work

These pipe bends are fitted with reaction bonded silicon carbide liners and are used to pneumatically convey minerals to fluidised bed reactors. The lining system has to be capable of coping with a rise in temperature of around 850 degrees C centigrade within a matter of seconds.

The system is designed to accept flexure of the steel bend casing without damaging the ceramic lining.

A fine grained reaction bonded silicon carbide has excellent thermal shock resistance, particularly those with a grain size of 10 microns or less and can be 5 to 10 times more wear resistant than 95% alumina ceramic.

Straight pipe, pipe bends, tee pieces, "Y" pieces and valves are fitted with reaction bonded silicon carbide liners.

Where the risk of thermal shock damage is low, 95% alumina ceramic linings are used.

95% alumina ceramic linings are approximately 10 times more wear resistant than ni-hard bends.

Reaction Bonded Silicon Carbide Fluidised Bed Reactor Bend

Rotary Valves

Fully sintered alumina, reaction bonded silicon carbide and sintered tungsten carbide ceramics are used to protect rotary valves from abrasion and corrosion caused through the handling of aggressive minerals and metals.

In very abrasive conditions an unlined valve might wear out within 2 months, whereas an alumina ceramic lined valve might last between 5 and 10 years, before the lining system requires regrinding. The ceramic lining system can be reground between 10 and 20 times.

Reaction bonded silicon carbide is sometimes used for the rotor radial seals and sintered tungsten carbide is used for the adjustable vane sealing blades in very extreme applications.

Usually 95% alumina ceramic is used to protect the valve bore, end plates and the sections of the rotor shaft that rotate in the stuffing boxes. Hardened tool steel is used for the vane sealing blades.

Alumina ceramic lined rotary valve
300mm Bore 95% Alumina Ceramic Lined Rotary Valve
Alumina ceramic hydrocyclones

Hydrocyclones

95% alumina and reaction bonded silicon carbide ceramics are used to manufacture hydrocyclones for separating abrasive minerals from liquids.

In applications where quartz, with a hardness rating of 1100 Vickers, is being separated from sea water, 95% alumina ceramic will erode quite quickly. Reaction bonded silicon carbide, within the same environment shows no visible wear, except an extremely high polish.

We have supplied ceramic hydrocyclone lining systems designed to operate at up to 10,000 psi.

40mm Bore x 95% Alumina Ceramic Hydrocyclones

Jet Mills

95% fully sintered alumina and reaction bonded silicon carbide are used to protect the internal surfaces of jet mills from high velocity erosion and corrosion.

In applications where a 6mm thick soft rubber lining lasts approximately 4 weeks, 6mm thick 95% alumina ceramic has lasted approximately 6 years.

Alumina ceramic jet mill lining
95% Alumina Ceramic Jet Mill Lining
Reaction bonded silicon carbide bearings

Bearings

Reaction bonded silicon carbide is used for the manufacture of high temperature bearings and operate without lubrication.

Reaction Bonded Silicon Carbide Bearings

Centrifuge Scrolls

Fine grained reaction bonded silicon carbide is used in the form of weldable wear tiles for centrifuge scrolls and is capable of achieving around 5 times longer than alumina or tungsten carbide ceramics.

Reaction bonded silicon carbide tipped centrifuge rotor
Reaction bonded silicon carbide tipped centrifuge rotor
Alumina ceramic lined cones

Cone Linings

Small to very large steel or concrete cones can be lined with hard wearing ceramic taper tiles. The system is ideally suited to large area cyclone, hydrocyclone, hopper and silo cones and utilises flexible adhesives to secure the tiles in position.

The cone shown opposite is approximately 500mm diameter at the large end and is to be welded on to a larger pressure vessel. The ceramic lining is to protect the steel cone from the abrasive effects of silicon metal and will operate at a constant pressure of around 100 psi. Initialy, the ceramic lined cone will be pressure tested to 235 psi.

95% Alumina Ceramic Lined Cone

A Comparison Between a 95% Alumina Ceramic and a 10 Micron Grain Sized Reaction Bonded Silicon Carbide.

95% alumina and a 10 micron grain size engineering grade reaction bonded silicon carbide are products of fine powder technology. Both materials can be formed using die pressing, isostatic pressing, extrusion and slip casting techniques.

Alumina ceramic is sintered in a kiln at temperatures of between 1350 degrees C and 1800 degrees C, depending on the alumina content and formulation. The resulting ceramic has a hardness of around 1100 to 1500 Vickers, a fracture toughness in the region of 3.7 to 4.3 Mpam1/2 and a bending strength of 340 to 390 Mpa. Densities fall between 3.7 and 3.85 grms/cc.

95% alumina ceramic is a common wear resistant ceramic which can offer wear resistance 60 times greater than EN8 steel and 10 times greater than ni-hard, cast basalt and hard faced plate.

All ceramics are brittle and heavy impacts can cause catastrophic failure of the ceramic matrix, but as part of a correctly designed system alumina ceramics can accept heavy impacts.

6mm thick alumina ceramic personal armour can stop between 5 and 7 bullets from a Kalashnicova AK47 high velocity assault rifle. We use 50mm thick alumina ceramic tiles to line run-of-mine chutes handling 150mm to 200mm coal and shale dropping from a height of 1 to 1.5 metres.

An engineering grade reaction bonded silicon carbide is processed in a vacuum kiln, where it is heated to a temperature of 1650 degrees centigrade. The ceramic is produced by infiltrating a silicon matrix to bond the carbide grains together. The silicon is introduced to the moulding, pressing, or extrusion during the firing process. Basically the component is fired in a bath of silicon. The silicon melts during the kilning process and migrates between the carbide grains, through capillary action, thus producing an excellent engineering ceramic (basically the carbide component sucks up the free silicon like a sponge). The fired ceramic contains approximately 15% free silicon.

Lower grade reaction bonded silicon carbide ceramics, which utilise carbide grains sizes of 150 micron and above - similar to those used to manufacture kiln furniture, utilise silicon vapour infiltration to produce the matrix.

Fine grain RBSC can have a hardness rating of 3000 Vickers, a thermal shock resistance which is approximately 10 times greater and a wear resistance between 5 and 10 times greater than a 95% alumina ceramic.


Omegaslate (UK) Limited, 2 Chirk Close,
Forest Gate, Kidderminster, Worcs. DY10 1YG. United Kingdom.
Tel: +44 (0) 1562 755 824 Fax: +44 (0) 1562 742 979
Email: info@omegaslate.com