Shot Peening & Laser Shock Peening
Also known as: Shot Peening, SP, Laser Shock Peening, LSP, Shot Blasting, Bead Blasting
Shot peening bombards a surface with small spherical media (steel shot, glass bead, ceramic bead, or cast iron) at controlled velocity, inducing a compressive residual stress layer 0.05–0.5 mm deep. This counters the tensile residual stresses inherent in as-built LPBF and DED parts — which are fatigue crack initiation sites. Laser Shock Peening (LSP) uses high-power pulsed laser beams (nanosecond pulse, confined plasma) to introduce compressive stresses 2–6 mm deep, significantly deeper and more uniform than conventional shot peening, without surface roughening.
Why AM parts need this
LPBF and DED parts contain high residual tensile stresses (often 200–600 MPa tensile at the surface) from rapid thermal gradients during solidification. These tensile stresses dramatically reduce fatigue life — as-built LPBF Ti-6Al-4V has ~30–50% lower fatigue strength than wrought. Shot peening or LSP converts surface stresses to compressive, restoring fatigue life. Studies show shot-peened LPBF Ti-6Al-4V achieves fatigue life within 10–20% of wrought equivalents (Prevey-2008, LSP Technologies publications). For aerospace AM structural components, shot peening or LSP is routinely specified alongside HIP in the post-processing chain.
Achievable surface finish
Typical input Ra
10 µm
Achievable Ra
0.8–2.5 µm
Shot peening slightly roughens the surface (Ra increases 0.5–2 µm). LSP causes minimal surface roughening. If tight Ra is also needed, electropolishing or superfinishing follows shot peening.
Key parameters
Ceramic (ZrO₂) for titanium and medical — no ferrous contamination. Glass bead: lighter impact, less roughening. Steel shot: aggressive.
AMS 2432 specifies shot peening intensity by Almen strip deflection. Higher intensity = deeper compressive layer.
100% = every point hit at least once. 200% = full double-pass. Aerospace typically requires ≥100% coverage.
LSP Technologies PROCUDO: up to 30 J/pulse. Higher energy = deeper penetration. Typical aerospace: 3–8 J.
Compressive stress depth with LSP vs. 0.05–0.5 mm with conventional SP. Advantage for thick-section AM aerospace parts.
Compatible materials
Limitations
- Conventional shot peening is a line-of-sight process — cannot reach internal channels or concave features
- Shot peening slightly increases surface roughness — incompatible as final step if smooth surface is required (sequence: peen → superfinish/EP)
- Over-peening (excess intensity/coverage) can cause surface damage and reduce fatigue life
- LSP requires capital-intensive laser equipment — service bureau cost is high vs. conventional peening
- Ferrous shot media is incompatible with titanium and medical stainless steel (contamination risk — use ceramic or glass bead)
Related tools
Providers
Wheelabrator Group (Norican)
Global leader in shot blasting and shot peening equipment — Wheelabrator (Norican Group) systems used post-AM for surface conditioning, compressive stress introduction, and oxide scale removal on metal parts.
Hvidovre, DK
LSP Technologies
US developer of Laser Shock Peening (LSP) systems and services — the PROCUDO® LSP platform extends fatigue life of AM metal components by introducing deep compressive residual stresses with a pulsed laser.
Westerville, OH, US
Guyson International
UK manufacturer of blast finishing, wash, and ultrasonic cleaning equipment — bead and shot blast systems widely used for surface conditioning and stress peening of AM metal parts.
Skipton, GB
AM Solutions (Rösler Group)
Dedicated AM post-processing brand of Rösler Group — automated mass finishing, blasting, and washing systems designed specifically for AM metal and polymer parts at production scale.
Untermerzbach, DE
Relevant standards
Almen intensity from AMS 2432C (standard tier). LSP depth data from LSP Technologies PROCUDO published results (manufacturer tier). Fatigue life improvement from Prevey-2008 (peer-reviewed).
All post-processing