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Engineering Design Guidelines

More design engineers are finding out that traditional views of "ceramics" don't apply to Hexoloy silicon carbide products. Hexoloy products are opening new areas of application and design possibilities that are impractical with ductile metals and lesser ceramic materials.

Hexoloy sintered alpha silicon carbide is produced by pressureless sintering ultra-pure submicron powder derived from the original Acheson process. This powder is mixed with non-oxide sintering aids, then formed into complex shapes by a variety of methods and consolidated by sintering at temperatures above 2000°C (3632°F).

The sintering process results in a single-phase, fine-grain silicon carbide product that's very pure and uniform, with virtually no porosity. Whether submerged in corrosive environments, subjected to extreme wear and abrasive conditions, or exposed to temperatures in excess of 1400°C (2552°F), Hexoloy sintered alpha silicon carbide will outperform other commercially available ceramics or metal alloys, including superalloys.

These properties, plus the others outlined here, make Hexoloy silicon carbide ideal for applications such as chemical and slurry pump seals and bearings, nozzles, pump and valve trim, paper and textile equipment components, armor and more.

Think of all the applications where the properties of Hexoloy silicon carbide materials can make a big difference.

It's hard.

Hexoloy silicon carbide is one of the hardest high performance materials available, second only to diamonds.

Hardness (Knoop): 2800 kg/mm2 at room temperature.

It's strong.

Actual use of Hexoloy silicon carbide parts indicates extremely high strength and excellent resistance to creep and stress rupture at temperatures up to 1650°C (3000°F) for sintered alpha silicon carbide.

Flexural strength (4 pt.): 55,000 psi (380 MPa) Fracture toughness: 4.20 x 103 lb/in2 x in½ Modulus of elasticity (RT): 59 x 106 lb/in2 (410 GPa)

It's light.

Hexoloy silicon carbide weighs less than half as much as most metal alloys, 40 percent as much as steel and about the same as aluminum.

It's dense.

Densities of fired parts are consistently in excess of 98 percent of the theoretical density of Hexoloy silicon carbide - 3.21 g/cm3. Density: 3.10 g/cm3 minimum.

It's wear resistant.

The extreme hardness and density of Hexoloy silicon carbide make it ideal for applications where parts are subject to high abrasion and sliding wear.
Specified wear rate (pin on disc): SiC vs. SiC 1 x 10-9 mm2/kg.
Coefficient of friction (pin on disc): SiC vs. SiC 0.2.

It resists corrosion, oxidation and erosion.

The high density, low porosity and chemical inertness of Hexoloy silicon carbide permit it to function in environments of hot gases and liquids, in oxidizing and corrosive atmospheres, and in strong acids and bases, even at extremely high temperatures.

It resists heat.

The high thermal conductivity of Hexoloy silicon carbide, combined with its low thermal expansion, produces excellent thermal-shock resistance far better than tungsten carbide, aluminum oxide and RB silicon nitride. These properties make it a promising candidate to replace ductile metals in high-temperature applications.

It can be formed into complex shapes.

New developments by Saint-Gobain researchers in the use of bonding agents and other additives now permit the mass production of complex shapes of Hexoloy silicon carbide by extrusion; pressure forming, with bidirectional or isostatic presses at room temperature; slip casting; and injection molding.

It requires minimum machining.

The as-fired surface finish of Hexoloy silicon carbide parts is excellent (about 64 microinches). This surface quality, combined with tight dimensional control, yields parts that should require little or no additional machining or finish grinding, depending on application.

It's up to you.

Where can you use Hexoloy silicon carbide materials? We hope the information on this Web site provides you with some new ideas. And we look forward to helping you explore the possibilities of applying this unique material to your particular requirements.