Gear Wear and Tear

Shot Peening of Gears changes: Residual stress distribution Superficial structure Surface layer's hardnesses Surface layer's microstructure

It is a common fact that friction and wear that takes place between two sliding surfaces are considerably dependent on the finish of the surface. In fact a surface's roughness strongly influences the coefficient of friction. That is the reason why overcoming of such friction, especially in Gears involves a stringent lubrication process. Good surface finishing technologies are there in for improving the gear performance. The basic objective is to find a very effective remedy for reducing gear wear and at the same time reducing the need for lubrication.

What does a Surface finish do?
Latest researches indicate that an improved part surface finish as in Gears can:

• Reduce pitting fatigue in gears.
• Enhance the bending fatigue life of Gear teeth.
• Effectively reduce amount of frictional losses that is inherent in power transfer system.

Shot Peening
Shot peening is typically a process that involves cold working. Here, the surface of a gear is bombarded with tiny spherical media that are known as shot. Every single piece of shot that strikes the material acts as a sort of tiny peening hammer. They impart the surface of gear a small indentation or a dimple.

For creating the dimple, the surface of the gear material should be tension yielded. What happens is that beneath the surface, the material tries to get back to its original shape. In that process, just below the dimple, a hemisphere of cold-worked material is produced. It shows highly stressed compression.



Advantages of Shot Peening of Gears
The shot peening of gears has been seen to improve gear performance by:

• Better lubrication
• Reduced fretting
• Reduce noise
• Reduce spalling
• Lower operating temperature
• Eliminates scoring
• Betters the strength of tooth root
• Improves the strength of tooth profile
• Reduces wear at tooth profile
• Reinforces the gear wheels that were affected by notches