Selecting the right shot peening media is the single biggest lever you have on fatigue life, surface integrity, and cost-in-use. While steel shot dominates most applications, alternatives such as glass beads, ceramic beads, and stainless steel shot can outperform in specific scenarios across aerospace, automotive, energy, and medical devices. The challenge is knowing when each media is the best fit — and why.

The most common media in shot peening are steel shot, glass beads, ceramic beads, and stainless steel shot. Choose based on target Almen intensity, surface finish, contamination risk, durability, and total cost-in-use.

If you choose media only by habit or price, you’re leaving performance on the table. This guide maps each media type to its strengths, applications, and setup rules so you can match media → part → KPI with confidence.

By the end, you’ll know what each media does best, how to set size and hardness to hit your Almen intensity and coverage, how standards affect selection, and how to balance performance vs. cost for repeatable results.

Why steel shot is the default media for shot peening

Steel shot is the default peening media because its spherical geometry produces overlapping dimples that build a stable compressive residual stress layer. Within steel shot, high-carbon, low-carbon, and stainless families serve different intensity and cleanliness needs.

Steel shot delivers high durability, stable Almen intensity, broad size ranges (S70–S930), and excellent fatigue-life improvement — ideal for automotive and heavy-duty aerospace parts.

Types

High-carbon steel shot. This media provides higher hardness and durability, enabling greater peening intensity and producing deeper, more stable compressive stress layers on the surface.

Low-carbon steel shot. This option delivers gentler impacts, making it better suited to thin-wall or notch-sensitive parts where minimizing surface damage is essential.

Cut wire shot. This media offers exceptional size and shape uniformity with very low breakage, ensuring highly consistent intensity and coverage when tight process repeatability is required.

Intensity & coverage

As media size and hardness increase, achievable Almen intensity rises and the compressive stress layer typically extends deeper.

Conversely, smaller media reach 100% coverage more quickly and leave a finer surface finish, though they generally produce a shallower compressive layer.

Typical applications

Steel shot peening is commonly applied to coil springs, gears, crankshafts, turbine blades, and other safety-critical fasteners where extended fatigue life and crack prevention are required.

When your KPIs are fatigue life, crack suppression, and stress-corrosion resistance, steel shot is the first choice.

When glass beads are the better choice for shot peening

Glass bead peening is preferable when you must introduce beneficial compressive stress while preserving a clean, smooth surface with minimal risk of contamination or surface damage. It is especially well suited to thin-wall parts and precision components made from aluminum or titanium, where a gentle, tightly controlled impact is required.

Glass bead peening provides gentle, clean impacts and a smoother finish, making it ideal for delicate aerospace components and medical instruments where minimal surface damage is essential.

• Characteristics. Glass beads have a lower density than steel shot, so they impart a softer impact that reduces the likelihood of imprinting or raising sharp stress concentrators on sensitive alloys.
• Surface finish. Glass bead peening typically leaves a brighter and finer surface than carbon steel shot, which helps when parts have tight dimensional tolerances or very limited allowance for post-finishing.
• Typical applications. Engineers often specify glass beads for aerospace housings, thin aluminum or titanium components, precision springs, and medical instruments where cosmetic appearance and surface integrity are critical.
• Trade-offs. Compared with steel shot, glass beads usually offer a lower intensity ceiling and a shorter media life, so they tend to consume faster and may increase media replenishment frequency.

When your priorities are a smooth finish, low contamination, and controlled compressive stress at moderate intensity, glass beads are the safer and more predictable choice.

When ceramic beads deliver superior results in demanding peening

Ceramic bead peening is the preferred option when parts require high peening intensity together with a fine, controlled surface finish and excellent chemical and thermal stability. It excels on superalloys, titanium, and corrosion-resistant stainless steels used in harsh environments where both durability and cleanliness are non-negotiable.

Ceramic bead peening achieves high intensity with a fine finish and outstanding stability, making it ideal for turbines, superalloys, and other critical aerospace components.

• Performance characteristics. Ceramic beads possess very high hardness and excellent sphericity, allowing them to deliver higher attainable Almen intensity and a deeper compressive stress layer while maintaining tight control over surface roughness.
• Environmental resistance. Their inert chemistry and thermal stability minimize staining, corrosion risk, and media degradation, which is especially valuable in hot sections, chemically aggressive service, or when downstream cleanliness is critical.
• Typical applications. Engineers specify ceramic beads for turbine buckets and blades, hot-section engine components, titanium airframe parts, medical implants made from corrosion-resistant alloys, and precision stainless components that must remain uncontaminated.
• Trade-offs. Ceramic beads are more expensive per kilogram than steel or glass, but their long recycling life, low breakage rate, and reduced contamination often lower the total cost-in-use for high-value parts.

When the process must combine high intensity, low contamination, and repeatable surface quality on demanding alloys, ceramic beads deliver the most reliable overall result.

Why stainless steel shot matters for clean, corrosion-safe peening

Stainless steel shot is the preferred media when peening must be non-contaminating and corrosion-safe, especially on stainless substrates and hygiene-critical components. By eliminating carbon-steel residue and free iron transfer, it preserves surface chemistry while still generating the compressive stresses needed to improve fatigue life.

Stainless steel shot enables clean, non-contaminating peening with strong compressive stress and corrosion resistance, making it ideal for stainless parts, food equipment, and medical devices.

• Contamination control. Stainless shot minimizes the risk of embedding carbon-steel fines or free iron into stainless surfaces, which helps prevent flash rusting, discoloration, and downstream corrosion.
• Surface integrity. The spherical geometry of stainless shot produces uniform dimples and consistent residual stress without leaving dark contamination marks, which reduces rework and preserves cosmetic quality on visible parts.
• Process compatibility. Stainless shot is well suited to facilities with strict cleanliness requirements, such as food processing, pharmaceutical, and medical device manufacturing, where ferrous contamination can jeopardize compliance or product safety.
• Performance balance. Modern stainless shot delivers Almen intensity and media life comparable to quality carbon steel shot, while its corrosion resistance keeps the blast/peen cabinet cleaner and extends maintenance intervals.
• Cost considerations. Although unit cost is higher than carbon steel shot, users often recover value through fewer rejects, reduced cleaning steps, lower contamination risk, and smoother audits in regulated environments.

When your peening program must protect surface cleanliness, corrosion resistance, and regulatory compliance without sacrificing mechanical performance, stainless steel shot is the most reliable and audit-friendly choice.

How to choose media size and hardness for your target intensity

Media size and hardness govern three outcomes at once: achievable Almen intensity, the depth of the compressive stress layer, and the resulting surface roughness. The goal is to reach saturation at the specified intensity while achieving 98–100% coverage and preserving the finish required for the part’s function and downstream processes.

Larger and harder media raise Almen intensity and deepen the compressive layer, while smaller and softer media accelerate coverage and yield a finer finish—so match size and hardness to the part’s thickness, alloy, and fatigue targets.

• Start from the part and specification. You should first confirm the required Almen intensity range, surface finish limits, and coverage target for the part family, then back-calculate media size and hardness that can meet those constraints with process margin.
• Consider thickness and alloy sensitivity. Thin sections and notch-sensitive high-strength alloys are better served by smaller or softer media, which reduce the risk of imprinting and localized overstressing while still achieving saturation.
• Balance intensity and finish. Larger or harder media will typically deliver higher intensity and a deeper compressive layer, but they also increase surface roughness; if the downstream process requires a fine finish, you should step down in size or hardness and adjust velocity or exposure time to meet intensity.
• Use velocity as a secondary lever. If size and hardness are fixed for tooling or inventory reasons, you can fine-tune intensity via nozzle pressure or wheel speed; however, you should verify changes with a fresh saturation curve to maintain compliance.
• Plan for coverage efficiency. Smaller media usually reaches 100% coverage more quickly and produces a more uniform texture; for complex geometries with recesses or fillets, you should prefer smaller media to improve line-of-sight accessibility and reduce peening time.
• Validate with Almen and surface checks. Every change in size, hardness, or speed should be confirmed on Almen strips and, where required, by measuring roughness and inspecting for surface defects before releasing production.

Reference table — illustrative guidance for size vs. target

Target outcome	Suggested media size (examples)	Typical parts	Practical note
Low–medium intensity with fine finish	S110–S230 or fine glass beads	Springs, thin aluminum/titanium components	Fast coverage and smooth texture with minimal imprinting
Medium–high intensity with balanced finish	S230–S390 or medium ceramic beads	Gears, shafts, fasteners	Useful compromise of depth, intensity margin, and finish
High intensity with deep compressive layer	S390–S660 or coarse ceramic beads	Heavy crankshafts, blade roots, large steel forgings	Monitor roughness and adjust velocity/exposure as needed

You will consistently hit your targets when you anchor selection to the part’s material and thickness, then tune size, hardness, and velocity together to achieve the specified intensity, coverage, and finish—and you verify each change with a documented saturation curve.

How media quality and standards ensure consistent peening results

Consistent shot peening results depend on media quality and process discipline just as much as on equipment settings. If sphericity, hardness, size distribution, and cleanliness are poorly controlled, the same program that once met intensity and coverage can drift out of compliance and undermine fatigue performance.

Use media that conforms to recognized specifications, control sphericity, hardness, size distribution, and cleanliness, and verify results with Almen intensity and coverage to ensure repeatable, audit-ready peening.

• Sphericity determines impact uniformity. Highly spherical media produces near-identical dimples, which stabilizes Almen intensity, improves coverage uniformity, and reduces the risk of stress risers that can initiate cracks.
• Hardness must sit within a defined window. Media that is too soft will cold-flow and lose effectiveness before saturation, while media that is too hard increases the risk of surface damage; a validated hardness band provides intensity margin without compromising finish.
• Size distribution drives consistency. A narrow, well-controlled size distribution keeps kinetic energy and dimple geometry predictable; excessive fines or oversize particles cause uneven intensity, slow coverage, and unnecessary wear.
• Cleanliness and contamination control are mandatory. Oils, dust, fractured media, and tramp metal alter impact behavior and can stain or embed into the surface, so you should maintain classification screens, magnetic separators, and media add-rate controls to keep the working mix within limits.
• Standards provide the common language. Media definitions and sizing are typically referenced to SAE J444 families, while media quality requirements for cast/cut-wire/stainless shot are covered by the AMS 2431 series; process requirements—such as establishing saturation curves, verifying Almen intensity, and confirming coverage—are defined in AMS 2430 (superseding legacy AMS-S-13165 in many programs).
• Blasting vs. peening specifications should not be mixed. ISO 11124/11125 govern metallic blast-cleaning abrasives and test methods for cleaning applications, but they do not replace peening process requirements; peening audits expect spherical media and intensity/coverage control aligned to the AMS framework.
• Documentation closes the loop. You should record incoming media certificates (chemistry, hardness, size), lot traceability, working-mix checks, Almen strip data, and coverage inspections so the program is defensible during internal quality reviews and external audits.

When you combine spec-compliant media with disciplined Almen and coverage verification, you turn shot peening from a best-effort operation into a repeatable, certifiable process that consistently delivers the compressive stresses your parts were designed to rely on.

How to evaluate cost-in-use and recycling before selecting media

Media selection is a balance of performance and economics. Don’t judge by unit price alone — evaluate recycling life, breakage rate, cleaning frequency, and downtime.

Total cost-in-use = media price × (life & breakage) + throughput impact + cleanliness/contamination cost + audit compliance.

• Steel shot. It offers a mid unit cost with a long recycling life and a high achievable intensity, making it the best all-around value for most peening programs.
• Glass beads. They deliver a superb surface finish with very low contamination risk, although their shorter media life means they are best reserved for finish-critical parts.
• Ceramic beads. They come with a higher unit cost but compensate through long recycling life, high intensity capability, and very low contamination, which makes them ideal for high-value parts and harsh service conditions.
• Stainless steel shot. It carries a higher unit cost, yet it often yields significant hidden savings by preventing contamination and resisting corrosion, thereby reducing rework and compliance risks.

📊 Cost–Benefit Comparison

Media	Unit Cost	Recycling Life	Achievable Intensity	Surface Finish	Contamination Risk	Best-Fit Scenarios
Steel shot	Medium	High	High	Medium–Good	Medium	General peening, automotive, heavy industry
Glass beads	Low–Medium	Low–Medium	Low–Medium	Excellent	Low	Aerospace/medical, thin-wall parts
Ceramic beads	High	High	High	Excellent	Low	Superalloys, high-temperature/corrosive service
Stainless steel shot	High	High	Medium–High	Good	Very Low	Stainless parts, food/medical equipment

Viewed through total cost of ownership (TCO), more durable or cleaner media often win on high-value parts or where compliance costs are meaningful.

What this means for your next shot peening run

Translating this guide into action means treating media selection as an engineering decision tied to your part’s material, thickness, target Almen intensity, coverage, and finish limits — not as a habitual purchase. Steel shot remains the best all-around choice when you need reliable fatigue-life improvement at a competitive cost, glass beads shine when surface integrity and cleanliness are paramount, ceramic beads lead on demanding alloys that require high intensity with low contamination, and stainless steel shot safeguards hygiene and corrosion control without sacrificing mechanical performance.

To execute confidently, follow a simple, auditable workflow.

• First, define your KPI envelope: the Almen intensity range, required coverage (typically 98–100%), and allowable surface roughness.
• Second, select the media family that aligns with those KPIs and the alloy’s sensitivity: steel shot for general strengthening, glass or ceramic beads for finish-critical or high-alloy parts, and stainless steel shot for non-contaminating peening.
• Third, tune size and hardness to balance depth of compressive stress with finish, using velocity (wheel speed/nozzle pressure) as a secondary lever.
• Fourth, verify changes with a saturation curve, confirm intensity on Almen strips, and measure coverage and surface condition before releasing production.
• Finally, sustain repeatability by controlling media quality (sphericity, hardness band, size distribution, cleanliness), maintaining the working mix, and documenting lots, settings, and inspection results.

If your operation also requires blasting, sequence the processes to get the best of both worlds: grit-blast first to achieve cleanliness and anchor profile, then shot-peen with spherical media to lock in compressive stress and extend fatigue life. Evaluate decisions through total cost-in-use rather than unit price alone, since media life, contamination risk, rework, and audit outcomes frequently outweigh the initial cost difference—especially on high-value parts.