Blasting and shot peening look like the same thing. From a subcontracting point of view, they are not.
Blasting: a visual result
In blasting, the result is assessed mainly visually: the degree of surface cleanliness and the roughness achieved.
You agree the grade, the work is done, verification is by comparison. The conversation is simple and the check is within reach.
Shot peening: a controlled result
Shot peening does not clean. It introduces compressive residual stress in the surface layer, to increase the fatigue strength of the part.
The effect is not visible. It is measured.
That is where the whole difference comes from: shot peening works to standards, with controlled parameters and documentation. Intensity is verified on test strips, coverage is inspected, and the process is recorded.
If your part goes into aerospace, requirements are stricter still, and the supplier must hold the corresponding qualifications.
What to ask, by operation
For blasting:
- What cleanliness grade do you guarantee and how do you verify it?
- What abrasive do you use and what roughness results?
- How do you avoid cross-contamination between materials — steel, stainless, aluminium?
The last one matters and is often ignored. Abrasive previously used on carbon steel leaves ferrous particles on stainless steel, which then rusts.
For shot peening:
- Which standard do you work to?
- How do you verify intensity and coverage?
- What documentation do I receive with the parts?
- Do you hold the qualifications my industry requires?
When it makes sense
Blasting is frequently subcontracted for small series, large parts or occasional jobs.
Shot peening is subcontracted even by large companies, because the equipment, qualifications and documentation demand a specialisation that a small volume cannot justify.
Related reading
- Sandblasting
- What Does Shot Peening Do? Process, Standards and Applications
- Shot peening standards: AMS2430, AMS2432 and NADCAP
- When to subcontract and when to buy the machine
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