Gear Coating

Gears transmit load through the contacting surfaces. It has been seen in spite of a proper design, installation, or maintenance, gears can fail because of the resultant fatigue in the working surfaces. Coatings are an economical means to extend the fatigue lives of gears. Coatings can engineer the surfaces to prolong the fatigue lives of the mechanical components. For example by applying a tungsten-containing carbon coating applied on Spur Gears have shown remarkable results. The gears have been found to be displaying high hardness, low friction, and good toughness.

Let's take the example of Pinions and see the results for coating as well as the uncoated pinions.


Load:1500 N/mm²	Load: 2000 N/mm²
Micropitting: around 20%	Micropitting: none

In Gears Coatings are primarily used to influence the near-surface properties like:

Surface hardness
Surface roughness
Friction coefficient
Oil wettability

Advantages of Gear Coating
The Coating of gears offers the following advantages:

Almost doubles the gear life.
Increases the power density by around 25 - 50 percent.
Drastic cut down in parasitic power losses to the tune of 10 percent reduction in the gear systems.
Gear tooth temperature reduction by around 10°C.

Types of Gear Coating
Though there are different types of material that are there for the coating of gears, but by far the metal coating remains one of the best choices. Newer techniques have come in the metal coating methods that are significantly improving the performance of gears. A two of the popular methods of metal coating are given below:

Metal Coating by Ion Plating: The excellent properties of ion plating has made it the preferred choice for highly sophisticated gears required for space applications, for example, such gears have been successfully ion plated with 0.12 - 0.2 µm of gold for a proper lubrication and to prevent any occurrence of cold welding in the gear pitch line. Ion plating are now applied commercially, for plating the aluminum on the aircraft landing-gear components. This helps to fight corrosion.
Metal Coating by Sputtering: In the process of metal coating by sputtering, there is application of solid-film lubricants along with a wear-resistant hard refractory compound. The main benefits of this type of metal coating is that they can be used on curved and complex shaped gears without a binder. Other advantages are strong adherence and controlled thickness.