Shot Peening Surface Treatment: Ultimate Guide – From Principles, Processes to Applications and Future Trends

Introduction – The Invisible “Armor”

In modern industrial manufacturing, especially in high-end fields such as aerospace, automotive, energy, and healthcare, the requirements for the performance of metal components have become increasingly stringent. These components not only need to function stably under extreme loads, high temperatures, and corrosive conditions, but also must be as lightweight as possible. Often, the failure of the parts does not result from their insufficient overall strength, but rather begins with a tiny crack at the surface or near the surface. These cracks continuously expand under alternating loads, eventually leading to fatigue fracture.

How to create an invisible “armor” for these key components to effectively prevent the emergence and expansion of cracks? Shot Peening surface treatment is the answer. It is not a simple cleaning or finishing process, but a highly precise and controlled science, and it is a key technology for enhancing the reliability and durability of metal parts. This article will take you deep into the world of shot peening, revealing how it “thousands of hammer blows” inject powerful vitality into metal components.

Basic Concepts of Shot Peening Surface Treatment

What is Shot Peening Treatment

Shot Peening is a cold processing technique that uses high-speed projectiles (such as steel balls, ceramic balls, or glass balls) to impact the surface of the workpiece, causing plastic and elastic deformation of the surface metal. This process introduces residual compressive stress in the material’s surface layer, thereby improving the fatigue performance of the metal.

The core of this method lies in “controlled impact”. By uniformly spraying the pellets, a uniform compression layer is formed on the surface of the part, preventing crack initiation and propagation.

The Difference Between Shot Peening and Sand Blasting

Sandblasting is mainly used for cleaning, rust removal and surface roughening.

Shot peening focuses on surface strengthening and improvement of fatigue resistance.

Sandblasting is mainly used to improve the appearance and the adhesion of the coating, while shot peening is employed to enhance mechanical properties.

The mechanism of action of shot peening surface treatment

Introducing residual compressive stress

When a metal material is subjected to high-speed projectile impact on its surface, it will undergo plastic deformation, and its internal structure will be compressed, forming a layer of residual compressive stress. This stress can counteract the external tensile stress, thereby effectively delaying the initiation of cracks.

Surface hardening

Repeated impacts will cause the material’s grains to become finer, increasing the surface hardness and thereby enhancing the anti-wear ability.

Crack inhibition and extension obstruction

If there are tiny cracks on the surface of the part, the compressive stress generated by shot peening can seal the crack tip and reduce the rate of crack propagation.

Enhance fatigue resistance

Research shows that parts that have undergone shot peening treatment can have their fatigue life increased by 30% to 500%. This is particularly important for high-load components.

Various types and techniques of shot peening process

According to the different ways of accelerating the shot, shot peening is mainly divided into the following types:

Centrifugal Wheel Blasting

This method utilizes a high-speed rotating wheel to project the projectiles through centrifugal force. It is highly efficient with low energy consumption and is suitable for large-scale and batch production, such as the processing of automotive leaf springs and spiral springs. However, its flexibility and uniformity of strength are relatively poor.

Pneumatic Peening

This process utilizes compressed air as the power source, accelerating the projectiles within the gun and spraying them onto the surface of the workpiece. It is the most commonly used and flexible manufacturing method. By adjusting the air pressure, the distance of the gun, and the angle, the intensity of the peening can be precisely controlled, making it highly suitable for strengthening complex shapes, internal holes, and localized areas. However, its drawback is high energy consumption and the potential generation of a large amount of dust.

Ultrasonic Peening

This is a relatively new technology that uses ultrasonic energy to drive the tool head to impact the surface of the workpiece at an extremely high frequency. It has the advantages of high energy density, deep deformation layer, and good surface finish, and is particularly suitable for processing precision parts and weld seams with surface roughness requirements.

Laser Shock Peening -LSP

Advanced technology. It utilizes high-power pulsed laser to generate plasma explosions on the surface of the workpiece. The shock wave from the explosion causes plastic deformation of the surface layer, thereby introducing residual compressive stress deeper into the material (up to 1-2mm, which is several times that of traditional shot peening). It is mainly used for the highest-end components such as aircraft engine blades and turbine discs. The equipment is expensive and the cost is high.

Wet Blasting / Liquid Blasting

The projectiles are mixed with water and then sprayed. The presence of water can effectively suppress dust, reduce the fragmentation rate of the projectiles, and provide a certain cooling effect on the workpiece. It is commonly used in situations where cleaning and strengthening are carried out simultaneously, as well as in environments with strict requirements for dust control.

Types of equipment for shot peening surface treatment

Rotary turret shot blasting machine – suitable for large quantities of circular parts.

Hook-type shot peening machine – for medium and large-sized complex parts.

Track-type shot peening machine – suitable for batch processing of small parts.

Robotized shot peening system – High precision control, suitable for aerospace fields.

Ultrasonic shot peening equipment – Combining ultrasonic energy, the strengthening effect is more significant.

The advantages of shot peening surface treatment

Improve fatigue life and strength.

The cost is relatively low and the process can be completed at room temperature.

Can be combined with other processes (such as surface coating, electroplating, heat treatment).

The application scope is wide, covering materials such as steel, aluminum, titanium alloy, and stainless steel.

It has good environmental performance and no chemical pollution.

Comparison of Shot Peening with Other Surface Treatment Processes

The wide application fields of shot peening technology

The application of shot peening technology is almost in all heavy industry fields:

Aerospace: This is the field where the requirements for shot peening technology are the highest and the application is the most extreme. Engine blades, turbine discs, compressor discs, gears, landing gear, fuselage structural components, weld seams, and almost all critical load-bearing parts must undergo shot peening treatment. Laser shot peening has achieved remarkable results in this field.

Automobile industry: Leaf springs, coil springs, torsion bars, gears, drive shafts, connecting rods, valve springs, etc. Shot peening is a standard process for ensuring the reliability of automotive suspensions and power systems.

Energy industry:Turbine blades, nuclear power components, gears and bearings of wind turbines, etc., all require shot peening to address the issue of high-cycle fatigue.

Medical devices: Artificial joints (such as hip joints and knee joints), bone plates, screws and other implants. Shot peening not only enhances their fatigue resistance, but also a suitable surface roughness is conducive to the growth of bone cells and enables biological fixation.

General manufacturing industry: Gears, shafts, oil well tools, molds, springs and all other components subjected to alternating loads.

The future development trend of shot peening surface treatment

Intelligence and Automation

Introduce robot shot peening to enhance efficiency and consistency;

Optimize the process through real-time monitoring and sensor feedback.

Green and environmentally friendly development

Use recyclable pellets;

Reduce dust and noise pollution.

Ultra-fine shot peening

The micro-impact peening technology is suitable for precision electronic components and medical parts.

Development of Composite Processes

Shot peening combined with laser treatment, heat treatment and coating achieves a synergistic effect.

Conclusion

Shot peening surface treatment is a science and art that perfectly combines macroscopic processes with microscopic mechanics. It achieves the “constructive” ultimate enhancement of the performance of metal materials through a seemingly “destructive” method. From every jolt of a car to every roar of an aircraft engine, there is reliable support provided by shot peening technology behind it.

With the advancement of Industry 4.0 and intelligent manufacturing, shot peening technology is evolving towards greater precision, intelligence and environmental friendliness. It is no longer merely an auxiliary process but an indispensable part of the product design chain. It is the core technological foundation for high-end manufacturing to achieve lightweighting, long lifespan and high reliability. Whether it is engineers, designers or quality control personnel, a deep understanding of the shot peening principle and mastery of its process control are crucial for manufacturing outstanding products.

CNC machining on demand

Start your project today. Get free DFM from professional engineer at ProtoTi.

Get instant quote