Silicon Nitride, Si3N4
Silicon nitride is a man made compound synthesized through several different chemical reaction methods. Parts are pressed and sintered by well developed methods to produce a ceramic with a unique set of outstanding properties. The material is dark gray to black in color and can be polished to a very smooth reflective surface, giving parts with a striking appearance. High performance silicon nitride materials were developed for automotive engine wear parts, such as valves and cam followers and proven effective. The cost of the ceramic parts never dropped enough to make the ceramics feasible in engines and turbochargers. The very high quality bodies developed for these demanding high reliability applications are available today and can be used in many severe mechanical, thermal and wear applications.
| .Key Properties | |
 | High strength over a wide temperature range |
| High fracture toughness |
| High hardness |
| Outstanding wear resistance, both impingement and frictional modes |
| Good thermal shock resistance |
| Good chemical resistance |
| . Typical Uses | |
| Rotating bearing balls and rollers |
| Cutting tools |
| | Engine moving parts — valves, turbocharger rotors |
| Engine wear parts — cam followers, tappet shims |
| Turbine blades, vanes, buckets |
| Metal tube forming rolls and dies |
| Precision shafts and axles in high wear environments |
| Weld positioners |
General Information
The material is an electrical insulator and is not wet by nonferrous alloys. Silicon nitride is a rather expensive material, but it's performance to cost benefit ratio is excellent in the applications where it can outperform the normally utilized materials with long life and very reliable low maintenance operation.
Engineering Properties*
| Silicon Nitride, Hot Pressed | |||
| Mechanical | SI/Metric (Imperial) | SI/Metric | (Imperial) |
| Density | gm/cc (lb/ft3) | 3.29 | (205.4) |
| Porosity | % (%) | 0 | (0) |
| Color | — | black | — |
| Flexural Strength | MPa (lb/in2x103) | 830 | (120.4) |
| Elastic Modulus | GPa (lb/in2x106) | 310 | (45) |
| Shear Modulus | GPa (lb/in2x106) | — | — |
| Bulk Modulus | GPa (lb/in2x106) | — | — |
| Poisson's Ratio | — | 0.27 | (0.27) |
| Compressive Strength | MPa (lb/in2x103) | — | — |
| Hardness | Kg/mm2 | 1580 | — |
| Fracture Toughness KIC | MPa•m1/2 | 6.1 | — |
| Maximum Use Temperature (no load) | °C (°F) | 1000 | (1830) |
| Thermal | | ||
| Thermal Conductivity | W/m•°K (BTU•in/ft2•hr•°F) | 30 | (208) |
| Coefficient of Thermal Expansion | 10–6/°C (10–6/°F) | 3.3 | (1.8) |
| Specific Heat | J/Kg•°K (Btu/lb•°F) | — | — |
| Electrical | |||
| Dielectric Strength | ac-kv/mm (volts/mil) | — | — |
| Dielectric Constant | — | — | — |
| Dissipation Factor | — | — | — |
| Loss Tangent | — | — | — |
| Volume Resistivity | ohm•cm | — | — |
| Silicon Nitride, Pressureless Sintered | |||
| Mechanical | SI/Metric (Imperial) | SI/Metric | (Imperial) |
| Density | gm/cc (lb/ft3) | 3.27 | (204) |
| Porosity | % (%) | 0 | (0) |
| Color | — | black | — |
| Flexural Strength | MPa (lb/in2x103) | 689 | (100) |
| Elastic Modulus | GPa (lb/in2x106) | 310 | (45) |
| Shear Modulus | GPa (lb/in2x106) | — | — |
| Bulk Modulus | GPa (lb/in2x106) | — | — |
| Poisson's Ratio | — | 0.24 | (0.24) |
| Compressive Strength | MPa (lb/in2x103) | — | — |
| Hardness | Kg/mm2 | 1450 | — |
| Fracture Toughness KIC | MPa•m1/2 | 5.7 | — |
| Maximum Use Temperature (no load) | °C (°F) | 1000 | (1830) |
| Thermal | | ||
| Thermal Conductivity | W/m•°K (BTU•in/ft2•hr•°F) | 29 | (201) |
| Coefficient of Thermal Expansion | 10–6/°C (10–6/°F) | 3.3 | (1.8) |
| Specific Heat | J/Kg•°K (Btu/lb•°F) | — | — |
| Electrical | |||
| Dielectric Strength | ac-kv/mm (volts/mil) | — | — |
| Dielectric Constant | — | — | — |
| Dissipation Factor | — | — | — |
| Loss Tangent | — | — | — |
| Volume Resistivity | ohm•cm | — | — |
*All properties are room temperature values except as noted.
The data presented is typical of commercially available material and is offered for comparative purposes only. The information is not to be interpreted as absolute material properties nor does it constitute a representation or warranty for which we assume legal liability. User shall determine suitability of the material for the intended use and assumes all risk and liability whatsoever in connection therewith.
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