Silicon Nitride Bearing Grade ceramic
The information provided in the above table is offered for comparison only, and is not to be constred as absolute engineering data or constituting a warranty or representation for which we assume legal responsibility.
Chemical Formula: Si3N4
Background
Silicon nitride (Si3N4) was developed in the 1960s and '70s in a search for fully dense, high strength and high toughness materials. A prime driver for its development was to replace metals with ceramics in advanced turbine and reciprocating engines to give higher operating temperatures and efficiencies.
Silicon nitride has better high temperature capabilities than most metals combining retention of high strength and creep resistance with oxidation resistance. In addition, its low thermal expansion coefficient gives good thermal shock resistance compared with most ceramic materials.
Key Properties
Applications exploit the following properties of silicon nitride:
- Low density
- High temperature strength
- Superior thermal shock resistance
- Excellent wear resistance
- Good fracture toughness
- Mechanical fatigue and creep resistance
- Good oxidation resistance
Ceramics offer many advantages compared to traditional materials. Their hardness and stiffness combined with heat, corrosion resistance, light weight, LOX compatible and non magnetic characteristics offer designers the ability to drastically improve on all aspects of performance leading them to be used in the following applications:
- high vacuum
- medical
- oil & gas
- research
- motorsport
- semi conductor industry
- nuclear
- defence
- aerospace
- renewable energy
Bearings
The wear resistance, low friction and high stiffness of fully dense silicon nitride improve the performance of high temperature unlubricated roller and ball bearings. Silicon nitride bearings have shown increased bearing life, better speed capability and greater corrosion resistance compared to conventional higher-density steel and hard metal bearings. Silicon nitride can be used in bearings in two ways:
A) For rolling elements only this type is known as a ‘Hybrid Bearing’. Applications
include machine tool spindles, vacuum pumps and sterilisable and unlubricated
dental drills.
B) For ‘Fully ceramic bearings’ this type of bearing has ceramic races and rolling
elements, the cage can be produced from ceramic material or alternatively PTFE,
PEEK or as a full compliment bearing. Applications for this type of bearing include
high vacuum, chemically corrosive environments and high temperature applications.
All ceramic bearings are used in applications where corrosion, electric or magnetic fields prohibit the use of metals. For example in tidal flow meters where seawater attack is a problem or electric field seekers.
Future Applications
There are continually growing numbers of applications where silicon nitride can be used to provide solutions to problems which were though of as impossible when using standard materials. Carter are able to offer small batch production of silicon nitride bearings and components with short lead times and competitive pricing allowing our customers to test and approve the products in their working environments without the need for costly large production runs.
| Item | Condition | Units | TSN-03NH | TSN-22H | |
|---|---|---|---|---|---|
| Density | JIS R 4108 | g/cm³ | 3.24 | 3.22 | |
| Colour | JIS R 1610HV, 20Kg | Black | Black | ||
M |
Hardness | 1,500 | 1,460 | ||
| Flexural Strength | JIS R 1601, 20°C 3 point bending |
MPa | 1,000 | 925 | |
| Young's Modulus | JIS R 1605, 20°C | GPa | 310 | 320 | |
| Compressive Strength | JIS R 1608, 20°C | MPa | >4000 | ||
| Poisson's Ratio | JIS R 1605, 20°C | 0.29 | 0.28 | ||
| Fracture Toughness | JIS R 1607 (Indentation) 20Kg, 30sec |
MPa√m | 7 | 6.3 | |
| T h e r m a l |
Thermal Expansion | RT -500°C JIS R 1618 |
10-6/°C | 2.7 | 2.5 |
| Thermal Conductivity | JIS R 1611 | W/m-°K | 20 | 27 | |
| Specific Heat | JIS R 1611 | J/Kg-°K | 680 | 670 | |
| Max. Thermal Shock | ΔTc, °C | 800 | 800 | ||
| Max. Service Temp. | °C | 1,000 | 1,000 | ||
| E l e c t r i c a l |
Dielectric Strength | 20°C | kV/mm | >14 | >14 |
| Volume Resistance | 20°C | Ω-cm | >1012 | >1012 | |
| Surface Resistance | 20°C | MΩ/5mm | >1014 | >1014 | |
