Shot Peening
Shot peening bombards a part's surface with controlled spherical shot to create a layer of compressive stress, which greatly improves fatigue life and resistance to stress-corrosion cracking. It is used on springs, gears, shafts, crankshafts and aerospace parts.
What it is
Unlike shot blasting, which cleans, peening is a controlled cold-working process. Intensity is measured with Almen strips, and coverage (typically 100–200%) is verified so the compressive layer is uniform.
Because fatigue cracks start at the surface under tension, compressive stress there delays crack initiation and growth.
Typical applications
- Coil and leaf springs
- Gears and splines
- Crankshafts and connecting rods
- Turbine blades and aerospace parts
- Welded joints (fatigue improvement)
Suitable materials
- Spring and alloy steels
- Carburised and hardened steels
- Aluminium and titanium alloys
- Stainless steels
Points to consider
- Specify Almen intensity, coverage and media size.
- Mask surfaces that must not be peened (threads, precision bores).
- Peen after heat treatment and before final assembly.
- Peening slightly roughens the surface.
Frequently asked questions
What is the difference between shot peening and shot blasting?
Shot blasting cleans surfaces. Shot peening is a controlled process that creates compressive stress to improve fatigue life.
How much does shot peening improve fatigue life?
Depending on part and loading, fatigue life can increase substantially, often several times.
How is shot peening controlled?
With Almen strips to measure intensity and inspection of coverage, according to the specification.