Shot peening is a special surface treatment that significantly increases the fatigue strength and service life of metal parts. Unlike conventional sandblasting, its purpose is not cleaning but hardening the surface layer by inducing beneficial compressive stresses.
What is shot peening?
Shot peening is a special blasting process in which the surface of a part is bombarded in a controlled way with shot (small balls of steel, ceramic or glass). Each impact acts as a small plastic deformation and introduces a compressive stress into the surface layer, resulting in much higher resistance and minimal wear in service.
How does shot peening work?
The effect is produced by transferring the kinetic energy of the shot to the surface, generating a layer of residual compressive stress. Cracks do not initiate or propagate in a zone under compression, and since almost all fatigue and stress-corrosion failures originate at or near the surface, shot peening delivers significant increases in service life.
What benefits does shot peening bring?
- increases resistance to stress by up to 80%;
- extends component life by up to 100%;
- reduces the risk of corrosion;
- improves tensile stress after machining and heat treatment;
- a fully reproducible, precise and controlled process.
Where is shot peening used?
Shot peening is frequently required in aircraft repairs and across the aerospace and automotive industries, for components subjected to constant loads.
Standards and compliance
All shot peening equipment is built to AMS2430 and AMS2432 and complies with NADCAP. Machines can be built to order according to each customer’s specifications.
Conclusion
Shot peening is essential where reliability and part life are critical. VIBROBLAST offers high-technology shot peening equipment compliant with the most demanding industrial standards.
What does shot peening do to metal?
Shot peening bombards a metal surface with small spherical media (steel shot, cut wire, ceramic or glass beads) so that each impact plastically deforms a tiny dimple. The overlapping dimples create a layer of compressive residual stress just below the surface. This compressive layer counteracts the tensile stresses under which fatigue cracks start and grow — which is why shot-peened parts last dramatically longer under cyclic load.
Unlike sandblasting, whose goal is cleaning or surface preparation, shot peening is a cold-working mechanical treatment: the goal is not appearance, but measurable改 fatigue life, resistance to stress-corrosion cracking and fretting.
How the process is controlled: Almen intensity and coverage
- Almen intensity — thin spring-steel strips (types N, A, C) are peened together with the part; their arc height tells you exactly how much energy the shot stream delivers. Typical aerospace specifications call out intensities such as 0.15–0.30 mmA.
- Coverage — the percentage of the surface covered by dimples. Critical parts require 100% coverage or more (e.g. 200% = double exposure time).
- Media control — size, hardness and roundness of the shot are checked continuously; broken media is removed, because sharp fragments damage instead of strengthening.
Standards: AMS 2430, AMS 2432 and NADCAP
Aerospace shot peening is governed by AMS 2430 (conventional peening) and AMS 2432 (computer-monitored peening), with process approval through NADCAP audits. These standards define media, intensity verification with Almen strips, coverage inspection, masking and documentation — and they are the reason serious suppliers invest in automated, instrumented machines rather than manual cabinets.
Where shot peening is used
- Aerospace — landing gear, turbine and compressor blades, structural fittings, gears.
- Automotive — coil and leaf springs, gears, connecting rods, stabilizer bars.
- Energy & heavy industry — shafts, welded joints (against stress-corrosion cracking), drill components.
Shot peening vs. sandblasting — the short answer
Both propel media at a surface, but sandblasting cleans and prepares (rust, paint, scale removal — typically with angular abrasives), while shot peening strengthens (spherical media, controlled intensity, measured coverage). A part can be sandblasted for coating and separately shot-peened for fatigue life — the two processes are complementary, not interchangeable.
Not sure which equipment fits your parts? A Vibroblast specialist visits your factory, analyses your parts and current process, and recommends the right solution — even if that means a cheaper machine than you expected.
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