Short Answer:

Shot peening is a mechanical process used to improve the surface properties of metal parts. In this method, small metal or ceramic balls (called shots) are blasted at high speed onto the surface of a component. This creates tiny dents or compressions, which introduce compressive stress on the surface. This stress makes the surface stronger and more resistant to cracks, fatigue, and corrosion.

Shot peening improves the fatigue strength, wear resistance, and overall durability of parts like gears, springs, and turbine blades. It is commonly used in automotive, aerospace, and heavy machinery industries to increase the life and performance of critical components.

Detailed Explanation:

Shot Peening and Its Effect on Surface Properties

In mechanical engineering, many components like springs, crankshafts, gears, and blades are constantly under repeated loading and stress. These stresses can lead to fatigue failure, cracks, and surface damage over time. To make these parts more durable, a technique called shot peening is used. Shot peening helps increase the strength and life of the parts by modifying the condition of their surface.

What is Shot Peening

Shot peening is a cold working process where the surface of a metal part is bombarded with small, round particles (called shots) at high speed. These shots are made from steel, glass, or ceramic. As each shot hits the surface, it creates a tiny dent or impression.

This denting action causes the outer layer of the material to compress, and this compression spreads slightly below the surface. As a result, residual compressive stress is created in the surface layer of the metal. This stress improves the surface strength and helps prevent damage from repeated loads.

Unlike polishing or grinding, which remove material, shot peening adds beneficial stress without changing the overall size or shape of the part.

How Shot Peening Improves Surface Properties

Increases Fatigue Strength
Fatigue failure happens when a part breaks after many cycles of loading and unloading. Shot peening creates compressive stresses on the surface that oppose the tension forces, making it harder for cracks to start or grow.
Reduces Crack Growth
Cracks usually begin on the surface where tensile stress is highest. Since shot peening puts the surface into compression, it delays or completely stops crack formation.
Improves Wear Resistance
The hard surface produced by shot peening makes the part more resistant to rubbing, sliding, or erosion, increasing its wear life.
Enhances Corrosion Resistance
Cracks are common entry points for rust and corrosion. By preventing cracks, shot peening helps protect parts from chemical attack and environmental damage.
Improves Strength Without Heat
Since shot peening is a cold process, it avoids the problems linked with heat treatment like warping or distortion.
Improves Surface Roughness
The process can help in reducing surface roughness or controlling it, which affects how well a part fits, seals, or operates.

Applications of Shot Peening

Automotive Industry:
Used in gears, suspension springs, connecting rods, crankshafts, and other moving parts.
Aerospace Industry:
Improves durability of turbine blades, landing gear, aircraft frames, and wing parts.
Heavy Machinery:
Applied to tools, shafts, chains, and hooks for improved life under tough conditions.
Medical Devices:
Applied on implants and surgical tools to make them more reliable and corrosion-resistant.

Benefits of Shot Peening

Extends the life of machine parts
Reduces need for repairs and replacements
Improves load-carrying capacity
Cost-effective surface enhancement method
Helps avoid sudden failures and breakdowns

Limitations of Shot Peening

Requires careful control of shot size, speed, and coverage
Not suitable for very thin or soft materials
May require masking to protect areas not meant to be peened
Needs special machines and safety precautions

Conclusion

Shot peening is a highly effective surface treatment that improves the strength, durability, and resistance of metal components. By creating compressive stress on the surface, it prevents cracks, enhances fatigue life, and protects against wear and corrosion. This process is widely used in industries where performance and safety are critical. When properly applied, shot peening can significantly extend the working life of essential mechanical parts without changing their shape or size.