Shot Peening and Its Benefits

Shot peening is a metal finishing process that is not only performed to restore the original shape of the metal but it is also useful for modifying its mechanical properties. This process makes use of velocity and mass of a shot stream for producing compressive residual stress at the surface of the part. Force is used to impact the surface, causing the surface zone material to yield as the metal grains are shaken into a more relaxed state. Due to the shaking, tensile stress is counteracted by the surface layer, preventing cracks and other damage.

Why Short Peen?

This procedure is mainly performed to increase the fatigue life of the part by bombarding its surface with small spheres of compressive stress-inducing media. It is very similar to using a ball peen hammer repeatedly on the surface of the part. This process is quite useful in improving the fatigue life of housings, shafts and gears.

Stress concentrations in the form of welds, burns and scratches are created internally with machining and forming of metal parts. These stress concentrations can result in additional defects in the parts, causing porosity, corrosion, premature fatigue failure or deteriorated strength. However, through peening, these problems can be easily prevented. Generally, fatigue cracks start at surface imperfections and a compressively stressed peened skin can easily help in prevention of crack formation.

A layer of compressive stress is introduced by peening which causes compacting of the material. Atoms on the metal surface become crowded and adjust to restore the original shape of the metal by pushing it outward. Atoms deep inside the metal are pulled towards the surface by their bonds. An internal tensile stress is created when the outward pull is resisted by the deeper atoms. This process keeps the part in equilibrium with compressive stress on the surface of the part.

Some Benefits of Shot Peen Procedure

• Improves strength of the metal parts
• Prevention of corrosion
• Increases gear life
• Increases life of drive pinion
• Increases life of crankshaft
• Prevention of hydrogen embrittlement
• Increases lubricity of metal by creating small pores for easy accumulation of lubricants
• Gives a uniform texture to the parts, ready for paint or coatings

Peening is used in various specialized processes such as flow treatment of pipes that are used in transportation of polymer pellets used in gas and oil industries.

Peening and Blasting are Different

Shot peen process should not be confused with shot basting procedure under which surface of an object is impacted with controlled stream of abrasive material. In peening, fatigue failure is prevented which originates on the part’s surface in the form of indentations. These indentations cause the metal to resist compression and create residual compressive stress.

Generally, blast wheels are used in the peening system for offering high flexibility, especially for large work pieces such as coil springs, connecting rods, wheels, air suspension beams and so on. There are many reliable manufacturers of shot peening equipment, shot blasting machines, dust collectors and manganese steel plates in India.

Summary

It is always recommended to choose a reliable manufacturer of shot peening equipment, shot blasting machines or manganese steel plates for optimum results.

Carlsen is a professional avid blogger who writes articles related to latest technologies