What You Need to Know About Shot Peening

Did you know that sandblasting can be used for shot peening? If you’re unsure what shot peening even is, don’t worry as we will cover everything you need to know about this complex process. Plus, learn about the benefits of shot peening and the equipment needed.

What is Shot Peening?

Shot peening is a cold work process or plastic deformation of metals below the recrystallization temperature (between 752-1292° F), used to produce a compressive residual stress layer. This process is designed to prevent fatigue by spreading a surface plastically which, in turn, changes the mechanical properties of the surface. Essentially, a metal surface is shot with particles to delay cracks and increase the metal’s lifespan.

How Shot Peening Works

Microscopic spherical shots of metallic, glass, or ceramic materials blast the surface of the metal. These shots act as a hammer by dimpling the surface. As the shots continue to hit the same spot, it forms an array of overlapping dimples. This constant “hammering” causes compressive residual stresses under each dimple. Compressive residual stress is the internal stress distribution locked into a material that creates a smaller volume.

Benefits of Shot Peening

Surface treatment procedures (bending and grinding) and heat treatment procedures create tensile residual stress, or internal force, that causes expansion. Tensile residual stress reduces the lifespan of metal because it causes premature metal fatigue, the weakening of a metal. This results in an accumulation of small cracks.

Shot peening converts tensile residual stress into compressive residual stress. Compressive stress reverses the negative effects of tensile stress. For example, a severely grinded metal that has been shot peened has double metal fatigue strength compared to a severely grinded metal that has not been shot peened. The benefit of shot peening is clear; it extends the life metal and prevents crack formation.

What’s the Difference Between Shot Peening and Shot Blasting?

Don’t let the similar names confuse you, shot peening and shot blasting have different functions. Shot peening shoots spherical shots to change properties of metal while shot blasting shoots steel beads to clean a metal’s surface. Shot peening improves a metal’s lifespan while shot blasting cleans and polishes metal.

Equipment Needed for Shot Peening

Below is a list of equipment generally needed for shot peening.

A blast machine is needed for shot peening. There are varying types of machines, but all use pressurized air to create blasting. To learn more about how a blast machine, read our blog post here.

A blast machine needs media valves to regulate the flow of abrasive.

The inlet and outlet valves are vital components of the blast machine setup. They determine whether a pot is pressurized.

Nozzles are needed to accelerate the abrasive out of the blast hose.

A blast machine also has various hoses: twin-line hoses, blast hose, and an 18-inch hose.

Last- but certainly not least- anyone who operates a blast machine needs to wear appropriate safety gear such as leather gloves, eye and hearing protection, abrasive-resistant clothing, and type-CE supplied-air respirator. Once you have all the equipment, your business is ready for shot peening!

Sources:

https://www.webpages.uidaho.edu/mindworks/Machine_Design/Posters/PDF/Peening_Poster.pdf

https://pdfs.semanticscholar.org/6fa2/7a1abc1ea2b94f094994ad4279295da87a08.pdf

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870011133.pdf