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Silicon
Nitride (Si3N4)
- Silicon
Nitride belongs to the group of non oxide ceramics which
have a special combination of characteristics i.e. extremely
high strength and tenacity, low thermal dilation, medium
thermal conductivity, high hardness and high chemical
resistance.
Silicon Nitride is therefor a superior material for use
in extreme mechanical and thermal conditions and when
reliability is paramount. Silicon Nitride is a dominant
material for a wide range of applications
- Material
Components of Silicon Nitride (Si 3N4) are produced from
a powder mix containing sintering aids. By kilning at
a high temperature, gas pressure and com-pression the
Silicon Nitride particles recristalyse in the form of
needles. A linking structure is therefor built which gives
the materials high strength and tenacity. Sintered parts
can be worked with diamond tools in order to obtain exact
dimension and the required surface finish.
Physical Characteristics:
| Silicon Nitride |
| PROPERTIES |
MEASUREMENTS |
| Main Characteristics |
High Temperature Strength Wear Resistant
Excellent Thermal Shock Resistance
Light Weight |
| Bulk Density |
2.50 g/cm³ |
| Flexural Strength |
50 Kpsi / 345 Mpa |
| Abrasion Resistance |
0.44 (1/cm³) |
| Vickers Hardness |
2900 kg/mm² (1 kg load) |
| Fracture Toughness |
3.0 Mpa x m 1/2 |
| Erosion Resistance |
10.0 x -6 cm³/g |
| Thermal Expansion |
4.5 x 10 -6 °C-1 |
| Thermal Conductivity at RT |
40 (W/mx °K) |
Quality control
A.F.B.M.A.* GRADE TOLERANCES AND TERMINOLOGY.
GRADE TOLERANCE CHART
- Basic diameter: The size ordered which is the basis
to which the basic diameter tolerances apply. The basic
diameter is specified by a fraction plus a decimal or
a decimal only to the sixth place. (example: 1/4'' + .0002''
or .2502'' - 15/64'' +
.0003'' or .234675'').
- Basic diameter tolerance:The maximum
allowable deviation of any ball diameter from the basic
diameter, in any shipments to fill orders for that basic
diameter.
- Diameter tolerance per ball: The permissible
difference between the largest diameter and the smallest
diameter measurable on one ball.
- Diameter tolerance per unit container:The permissible range of the average diameters of the
individuals balls within any one unit container.
- Grade: The numerical value of the diameter
tolerance per ball expressed in a millionth of an inch.
- Marking Increments: The standard unit
steps in a millionth of an inch used to express the specific
diameter.
- Some materials prevent us from obtaining a better result
of tolerance than those obtained at level 10. On the other
hand, some materials, mainly ceramics, make it possible
to obtain dimensions with a level 4 or 5 , RA is then
higher than in the above table.
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