Materials

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Ceramic Balls

Modern engineering ceramics are being used in increasing volumes throughout manufacturing industry. They offer a range of interesting and often valuable properties that are difficult or indeed impossible to achieve with other materials. The nature of these materials, particularly the combination of hardness and stiffness, makes them ideally suited to the production of high-precision balls. Three materials have attracted particular attention for ball manufacture:

Silicon Nitride

Combining hardness and toughness with low mass, silicon nitride offers significant advantages in high speed bearing applications, and for these reasons it is finding increased application in arduous bearing applications such as machine tool spindles and vacuum pumps. Increasing use and production volumes have dramatically reduced the once astronomic cost of the material so that silicon nitride balls can offer extremely cost-effective solutions to common industrial problems.

Alumina (Aluminium Oxide)

Alumina is used in 2 forms for ball production:

 Fused Ceramic - Alumina balls range in colour from almost white to a creamy yellow colour. The material is very hard, but less tough than either silicon nitride or alumina. Structurally the balls perform well, but they are prone to localised surface damage, which ultimately promotes failure. Alumina balls are widely used medical applications, particularly for replacement hip joints, and in valves and pumps for aggressive chemical environments.

 Single Crystal (Synthetic Ruby and Sapphire) - Single crystal alumina is widely use as a contact point for measuring equipment, and in this application provides good wear resistance at an effective price. Sapphire balls are clear, perhaps with a blue tint, and are far less common than ruby, which range in colour from almost clear to dark red. Balls are often supplied with drilled holes for mounting purposes.

Zirconia (Zirconium Oxide)

Zirconia in its partially stabilised form offers a number of useful properties. It can withstand very high temperatures without deterioration, it has a similar rate of thermal expansion to steel, it has a high toughness, and it is relatively inexpensive. It does have a tendency to porosity, which can prompt failure in some circumstances and tends to make it unsuitable for high stress applications, but it is widely used in pumps and valves for aggressive environments, and for measurement standards.

Ceramic Materials

Ball shapes are made in other ceramic materials, usually for very specific applications. Cubic zirconia balls are used as lenses in some specialised fibre-optic systems, but they are not generally available. Silicon carbide is interesting for some applications, particularly in its "conductive" forms, but its inherently low toughness makes ball production difficult and consequently expensive.

Steel Balls

Of all of the precision balls produced, probably more than 90% are steel, and the bulk of these are chrome steel. The scale of production is such that steel balls provide the most cost-effective solution for all applications where their properties are appropriate. Our steel types include:

 Steel

Chrome Steel

          - AISI 52100, 100cr6 SUJ2, EN31B, and 1.3505 

Stainless Steel 

          - 440C, 420, 316, and 304

Other Steels

          - High Speed Steel

          - Carbon Steel

          - Mild Steel

Tungsten Carbide Balls

Tungsten carbide, or more correctly cemented tungsten carbide, is strictly a "cermet" - ceramic metal combination, where particles of ceramic, tungsten carbide, are bonded together in a metal matrix. Originally produced as a cutting tool material - a market which it now dominates, Tungsten Carbide is widely used where hardness and high wear resistance is required. Variation in the binder percentage and the size of the carbide particles allows fine control over the properties of the material, hardness reducing and toughness increasing with increasing binder content. The binder material also contributes to the overall properties of the material. The two most common types are:

Cobalt Binder Tungsten Carbide

By far the most common form of Tungsten Carbide, Cobalt binder material is made in a range of compositions with up to 25% binder. Balls are generally made of material with 6% binder content. It is susceptible to corrosion of the cobalt binder, particularly in contact with water, and although this rarely results in structural failure it can cause severe degradation of the ball surface.

Nickel Binder Tungsten Carbide

Nickel binder tungsten carbide is far less common than cobalt binder material; it is not made in the same range of composition, and tends to be slightly softer. However, it offers significantly better resistance to corrosion. It is particularly useful in valve and pump applications, and it performs well in more aggressive chemical environments.

Other Materials

Apart from the materials discussed separately, balls are made as standard in a variety of other materials. Some of the more common materials are listed here:

Satellite (Cobalt Chrome)

Satellite balls are made in a small range of sizes, and are used in a number of specific applications. The material provides a useful combination of properties in that it is metallic, conductive, non-magnetic, has good hot hardness, shock resistance, and corrosion resistance. Where precision balls are required with combinations of these properties, satellite often offers the most effective solution.

Titanium

Used for a number of medical applications, body jewellery, and some industrial applications, titanium balls are available in a small range of sizes. The low hardness ~40 HRC limits the precision to which balls can be made, but where other properties of titanium are necessary, they can often be used effectively. Titanium balls can be supplied in medically approved grades and for decorative applications, supplied with a coloured surface.

Brass and Bronze

Brass and bronze balls are made in a good range of sizes, and are often used in gas applications where non-sparking materials are specified. They are also used in decorative applications.

Further Materials

Other materials include:

 Copper

 Aluminium

 Glass

 Plastics

 Nylon

 Delrin

 PTFE (Teflon)

 Phenolic

 BUNA

 Polypropylene

 Rubber

Get in touch with us to discuss the materials we use when fabricating industrial precision balls.