Engineering application map

Shot peening applications by industry

Controlled shot peening is used on selected metal components where fatigue performance, resistance to surface crack initiation or the near-surface stress state matters. Find your industry, recognise a component or loading problem, and see what SP Center needs for an initial feasibility review.

Send us your drawing Discuss your component with a shot peening engineer

What controlled shot peening is intended to do

Controlled shot peening directs specified media at a component surface under controlled conditions. Repeated impacts plastically deform a thin surface layer and can establish compressive residual stresses at and below the surface. For a suitable component and a qualified process, that stress state can reduce the effective tensile part of a cyclic load near the surface and delay surface crack initiation.

Shot peening is not shot blasting. Controlled shot peening is a fatigue-related special process in which media condition, intensity, coverage, exposure, access and records are controlled. Shot blasting is primarily used for cleaning, descaling or surface preparation. Similar equipment does not make the purposes or acceptance criteria interchangeable.

Suitability depends on the material, heat treatment, geometry, surface condition, load mode, critical zone, required fatigue performance, manufacturing sequence and the governing drawing or specification. Almen intensity and coverage are process controls, not stand-alone proof that a component will meet its fatigue requirement. Learn more about Almen intensity, coverage, media selection and control, compressive residual stress and how shot peening affects fatigue life.

Typical component candidates

Gear

Potential engineering purpose: improve resistance to fatigue crack initiation at a highly stressed tooth root; in some qualified applications, the surface condition of the flank is also part of the assessment.

Inputs needed: gear material, case treatment, final machining sequence, tooth-root geometry, treated and excluded zones, invoked specification, intensity, coverage and surface limits.

Guide: Gear shot peening

Shaft or axle

Potential engineering purpose: support bending or torsional fatigue performance at fillets, shoulders, keyways, splines and diameter transitions.

Inputs needed: load mode, critical location, material and heat treatment, radii, fits and bearing or seal surfaces that must be protected.

Guide: Shaft and axle shot peening

Spring or torsion bar

Potential engineering purpose: improve fatigue performance under repeated deflection or torsion when the material state, surface and process are suitable.

Inputs needed: spring type, wire or section size, material, heat treatment, presetting or stress-peening route, operating stress, critical surface and applicable spring specification.

Guide: Spring shot peening

Crankshaft or connecting rod

Potential engineering purpose: address fatigue-critical fillets, transitions or rod surfaces exposed to repeated bending and inertial loading.

Inputs needed: exact treated zone, machined and bearing surfaces, material condition, masking, dimensional limits and production approval requirements.

Compressor or turbine component

Potential engineering purpose: strengthen a specified fatigue-critical surface or fretting-prone feature on an approved component route.

Inputs needed: alloy, feature map, edges and thin sections, cooling holes, coatings, repair history, OEM specification, approved source requirements and inspection plan.

Spline, thread or local transition

Potential engineering purpose: reduce the adverse influence of a surface stress concentration under cyclic load.

Inputs needed: root radius, access, media size, masking boundary, fit or contact function, surface finish and proof that the chosen process does not damage the feature.

Automotive

Automotive powertrain, chassis and spring components can combine high production volume with repeated bending, torsion or contact loading. Shot peening is commonly considered where fatigue cracks may initiate at the surface of a root, fillet, spline or transition and where the process can be controlled consistently at production rate.

Typical candidates and loading reasons

axle shafts, half-shafts and drive shafts: cyclic torsion, bending and stress concentration at splines or diameter changes;
transmission and gearbox shafts: torsion and bending at shoulders, fillets, oil holes, keyways or spline run-outs;
gears, pinions and selected differential components: bending fatigue at tooth roots and application-specific contact-fatigue concerns;
crankshafts and connecting rods: repeated bending and inertial loads at fillets or section changes;
suspension springs, valve springs and torsion bars: high-cycle deflection or torsion;
selected steering and suspension parts: surface-initiated fatigue at highly stressed features, subject to drawing approval.

Engineering problems: tooth-root bending fatigue, shaft torsional or bending fatigue, high local cyclic stress, spline and fillet stress concentration, surface tensile residual stress after prior processing, and crack initiation at fatigue-critical transitions.

Why shot peening may be used: a qualified process can introduce a controlled near-surface compressive residual-stress field in the specified zone. The production case must still account for roughness, heat-treatment response, subsequent machining, residual-stress stability and the actual load spectrum.

Qualification and production considerations: define masks and no-peen zones; qualify media, Almen intensity, coverage and exposure; prove access to roots and splines; monitor repeatability and media condition; establish traceability; and support the customer’s FAI or PPAP process-evidence route, control plan or specific approval route where invoked. SP Center’s IATF certificate has a live stated scope for shot blasting, so confirm the certified scope and customer approval applicable to the proposed shot peening order rather than assuming coverage.

Have a similar part? Send the drawing, annual volume and known process requirements for preliminary review.

Aerospace

Aerospace shot peening is normally drawing-, specification- and approval-driven. Fatigue-critical geometry, fretting interfaces, thin edges, surface damage limits and traceability can be as important as the nominal process parameters.

Typical candidates and loading reasons

compressor blades and selected turbine or compressor components: cyclic and vibratory loading at specified airfoil, root or attachment features;
discs and shafts: fatigue-critical bores, fillets, holes or transitions where the approved design calls for peening;
gears and transmission components: tooth-root bending, spline or shaft fatigue;
landing-gear components: repeated landing and taxi loads at approved surfaces, bores, fillets or transitions;
springs and highly loaded mechanical or structural parts: surface-initiated fatigue or fretting fatigue at named zones.

Engineering problems: high-cycle fatigue, fretting fatigue, local bending, stress concentration, machining-related tensile residual stress and crack initiation at roots, fillets, holes or transitions.

Why shot peening may be used: controlled shot peening can form part of an approved fatigue design or repair route by changing the near-surface residual-stress state. It does not repair an existing crack, replace customer-specified inspections outside SP Center's service scope or authorise treatment of an unlisted feature.

Qualification and production considerations: use the current drawing and complete invoked specification; verify customer and approved-source status; control tooling, masks, media, intensity, saturation evidence where required, coverage and part handling; preserve edges, holes, thin sections and functional surfaces; maintain configuration and lot traceability; and supply FAI/AS9102 evidence when contractually invoked. Nadcap applies only where required and within an accredited scope. SP Center’s certificate page should be consulted for the current certified scope. See aerospace shot peening components, documentation and traceability.

Planning a new or transferred process? Discuss the component and approval route with SP Center before fixing production parameters.

Defence

Defence applications often combine cyclic mechanical loads with controlled drawings, restricted data, source approval and demanding traceability. The relevant question is not whether the equipment is “defence,” but whether a named metallic feature has a fatigue mechanism that controlled shot peening can address within the authorised route.

Typical candidates and loading reasons: drive-train shafts, gears, pinions, transmission parts, springs, suspension elements and other highly loaded mechanical parts with fatigue-critical fillets, splines, roots or transitions.

Engineering problems: bending and torsional fatigue, stress concentration, fretting at mechanical interfaces, cyclic loads and surface crack initiation.

Why shot peening may be used: the process may support the fatigue performance of a specified surface by introducing compressive residual stress. The design authority must define or approve the requirement, treated zone and acceptance evidence.

Qualification and production considerations: contract and export-control handling, configuration control, approved sources, masking, process qualification, inspection, traceability, nonconformance control and customer release. A company-level defence status does not replace product or process approval.

For a controlled preliminary review, send the non-restricted drawing information, material, specification and approval constraints through the RFQ channel.

Energy and power generation

Power-generation components can experience long operating periods, start-stop cycles, vibration and rotating loads. Controlled shot peening may be relevant where the assessed failure mechanism involves a surface or near-surface fatigue-critical zone.

Typical candidates and loading reasons: selected turbine and compressor components, shafts, couplings, gears, springs, transmission parts and rotating mechanical elements with fatigue-critical bores, fillets, keyways or transitions.

Engineering problems: high-cycle fatigue from vibration, low- or medium-cycle start-stop loading where surface initiation is relevant, torsional and bending fatigue, fretting fatigue and local cyclic stress.

Why shot peening may be used: the process can modify the residual-stress state in a defined accessible surface. It cannot compensate for creep, bulk material degradation, thermal damage, an existing crack or a failure mechanism governed away from the treated layer.

Qualification and production considerations: alloy and heat-treatment state, operating temperature and possible stress relaxation, repair history, coating sequence, critical-zone access, protection of fits and sealing surfaces, OEM or operator approval, process records and maintenance traceability.

Have a rotating component or repair route to assess? Send the drawing and known service condition.

Oil and gas

Oil and gas equipment can combine cyclic pressure, rotation, bending or torsion with aggressive service environments. Shot peening should be considered only after separating the mechanical fatigue mechanism from corrosion, environmental cracking, wear, erosion and material-compatibility questions.

Typical candidates and loading reasons: selected shafts, pump components, valve components, drive-train parts, drilling-related mechanical components, rotating parts, threaded or fatigue-critical regions, and high-stress transitions when a drawing or qualification route permits treatment.

Engineering problems: bending or torsional fatigue, local cyclic stress at threads, fillets and shoulders, fretting at interfaces, and surface crack initiation under combined mechanical loading.

Why shot peening may be used: a qualified compressive residual-stress field may support mechanical fatigue performance at a selected zone. Shot peening does not automatically prevent stress-corrosion cracking, corrosion fatigue, hydrogen damage or general corrosion. Material, environment, surface contamination, coating and operating conditions require separate evaluation.

Qualification and production considerations: material grade and hardness, sour-service or environmental requirements, cleanliness and contamination control, threads and seal surfaces, customer-specified inspections outside SP Center's service scope sequence, coating or plating sequence, dimensional limits, repair status, customer specification and traceability.

To screen an oil and gas part, send the drawing, material, environment and failure information if available.

Railway

Railway axles, springs and drive components operate under repeated loads over long service periods. Any shot peening proposal must fit the controlled product, maintenance and approval route and must protect wheel, bearing, fit and inspection functions.

Typical candidates and loading reasons: selected axle bodies and transitions, shafts, gears, springs, suspension parts, transmission components and other fatigue-critical mechanical features.

Engineering problems: rotating bending fatigue, stress concentration at fillets or transitions, fretting or press-fit influence, cyclic suspension loading and surface damage interacting with fatigue.

Why shot peening may be used: controlled shot peening may reduce effective tensile stress near an approved surface and delay crack initiation. It does not make a corroded, cracked, impact-damaged or thermally damaged railway part acceptable.

Qualification and production considerations: exact component and maintenance status, steel and heat treatment, critical and excluded zones, customer-specified inspections outside SP Center's service scope before and after as required, masking of bearing seats and functional surfaces, roughness and dimensional limits, full-scale or representative validation, railway approval and lot or serial traceability.

Evaluating an axle, gear or spring? Share the controlled drawing and maintenance context.

Heavy industry and industrial machinery

Large drives and production machinery can develop fatigue damage at geometric transitions under repeated torque, bending, impact or press cycles. Component size alone does not determine suitability; access, handling, failure mechanism and the ability to qualify the critical zone do.

Typical candidates and loading reasons: large shafts, gears, pinions, axles, springs, press and transmission components, couplings and cyclically loaded drive parts.

Engineering problems: bending and torsional fatigue, tooth-root fatigue, stress concentration at shoulders and keyways, cyclic press loading and fretting at drive interfaces.

Why shot peening may be used: local or full-zone treatment may support fatigue performance without changing nominal geometry, provided the material, surface and process route are suitable. The process should follow failure analysis rather than be added as an assumed cure.

Qualification and production considerations: component mass and handling, nozzle or wheel access, fixtures and rotation, masking, zone boundaries, media recovery, stable intensity and coverage, trial pieces or representative geometry, dimensional checks, production volume and repair approval.

For a large or unusual geometry, send a drawing, photographs and handling data.

General mechanical and precision engineering

Controlled shot peening can be evaluated for fatigue-critical machined parts outside a named sector. The strongest candidates have a known surface-initiated fatigue risk, an accessible critical zone and a material condition that can tolerate the selected process.

Typical candidates and loading reasons: heat-treated shafts, gears, springs, carburized parts, selected nitrided parts, precision mechanical parts with highly stressed fillets, splines, threads, holes or section changes.

Engineering problems: high local cyclic stress, bending or torsional fatigue, notch sensitivity, machining-induced tensile stress and fatigue crack initiation near the surface.

Why shot peening may be used: controlled peening can combine near-surface compressive residual stress with local cold work. Carburized and nitrided layers respond differently; neither treatment makes shot peening automatically beneficial. Surface hardness, case integrity, roughness, media hardness, sequence and representative fatigue evidence matter.

Qualification and production considerations: material certificate, exact heat-treatment route, final machining and coating sequence, surface and dimensional limits, access, masks, media selection, intensity, coverage, trials, inspection and change control.

Not sure which parameters to specify? Send the information you have. SP Center can review the gap and discuss the next qualification step without requiring a complete peening specification at first contact.

Engineering problem → component → shot peening decision

Engineering problem	Typical component examples	Why shot peening may help	Important qualification note
Surface fatigue crack initiation	springs, shafts, connecting rods, blades	A compressive residual-stress field can reduce effective near-surface tensile stress under part of the load cycle	Confirm that cracks actually initiate in the treatable surface and validate for the material and load spectrum
Bending fatigue	gear roots, axle transitions, crankshaft fillets	Treatment can target a high-stress surface feature where bending cracks often start	Prove root or fillet access, surface condition, coverage and representative fatigue performance
Torsional fatigue	drive shafts, half-shafts, torsion bars, splines	Controlled peening may improve resistance to shear-related surface crack initiation at a critical zone	Define the loaded zone and protect fits, journals and seal surfaces
Fretting fatigue	blade attachments, splines, fitted shaft regions	Near-surface compression may help where fretting and cyclic stress interact	Shot peening does not remove the contact cause; interface design, finish, lubrication and approval remain separate
Geometric stress concentration	fillets, shoulders, holes, threads, keyways	Local treatment may address the surface at a notch without adding material	Media must reach the feature at a qualified angle without damaging edges or dimensions
High local cyclic stress	landing-gear features, valve or pump transitions, press parts	A specified surface layer can be strengthened where changing the overall geometry is difficult	Obtain design-authority approval and demonstrate that the actual failure mechanism is surface-related
Fatigue-critical gear root	spur, helical, bevel and selected internal gears	Root compression may support tooth-root bending fatigue performance	Case treatment, root finish, media size, masking and subsequent finishing must be controlled
Fatigue-critical fillet or shaft transition	axles, transmission shafts, crankshafts	The process can target the surface at a bending or torsional hotspot	Avoid untreated bands; verify transition coverage and protect adjacent functional surfaces

Is my component a candidate for controlled shot peening?

A component justifies an engineering screening when one or more of the following statements is true:

fatigue cracks initiate at or near an accessible surface;
the component sees repeated bending or torsion;
a tooth root, fillet, spline, thread, hole, shoulder or section transition creates a local stress concentration;
a defined surface zone is fatigue-critical;
the load must be carried without adding material or materially changing the geometry;
the drawing, customer standard or repair instruction calls for shot peening;
a new design or process transfer needs fatigue and process validation;
the material, heat treatment and surface condition are known well enough to plan representative trials.

This checklist is a screening guide, not a process specification. A positive answer means that a review may be worthwhile; it does not establish media, intensity, coverage, process sequence or acceptance.

When shot peening may not be the right answer

Shot peening is not a universal fatigue remedy. Do not specify it until the likely failure mechanism and manufacturing route are understood.

The material is brittle, damaged or in a condition that cannot tolerate the intended surface deformation.
Cracking is driven by a bulk, subsurface, thermal, creep, corrosion, wear or overload mechanism that the treated layer cannot address.
The critical surface cannot be reached or inspected with adequate repeatability.
The drawing, customer or repair authority does not permit the process.
Existing cracks, grinding burn, corrosion pits or impact damage require detection and disposition rather than concealment.
Roughness, dimensions, edges, fits, sealing surfaces or cosmetic requirements are incompatible with the proposed treatment.
A later grinding, machining, heat-treatment or coating step would remove or alter the qualified layer.
The component needs engineering validation before any production claim can be made.

Failure analysis should identify the mechanism before shot peening is proposed as corrective action. Excessive or poorly controlled exposure can also be harmful; more intensity or more coverage is not automatically better.

Need capacity without building the process in-house?

SP Center can evaluate standard outsourcing, dedicated capacity, customer-owned equipment operated at SP Center, hybrid arrangements, and SP Center equipment and personnel at the customer site. The viable model depends on volume, equipment, qualification, data ownership, logistics and customer approval. Review the outsourcing options without duplicating the full outsourcing discussion here.

What to send for an initial review

Send what is available. You do not need to know every shot peening parameter before contacting SP Center.

component drawing and revision;
material and heat treatment;
annual volume and typical batch size;
current process route and final surface condition;
known failure mechanism, crack location or test result, if available;
customer specification or required shot peening standard;
target intensity and coverage, if already defined;
critical treated zone, masked surfaces and dimensional or roughness limits;
prototype, transfer, repair or serial-production status;
PPAP, FAI, traceability or approved-source requirements.

If the parameters are not defined, SP Center can review the available evidence and discuss feasibility, trials and the next qualification steps.

Send us your drawing Discuss the component with a shot peening engineer

Frequently asked questions about shot peening applications

Which components are commonly shot peened?

Common candidates include selected gears, shafts, axles, springs, torsion bars, crankshafts, connecting rods, compressor or turbine features, landing-gear parts and other fatigue-critical metallic components. The drawing, material, surface and load determine whether a specific part should be peened.

Which automotive parts can use shot peening?

Automotive applications can include gears, pinions, axle shafts, half-shafts, transmission shafts, crankshafts, connecting rods, suspension or valve springs and torsion bars. The relevant zone and production controls must be defined for the specific part.

Which aerospace components are shot peened?

Specification-driven applications can include selected compressor blades, discs, shafts, gears, transmission parts, springs and landing-gear features. Aerospace processing requires the current invoked requirements, customer or source approval and full traceability.

Why are gears shot peened?

Gears are often evaluated for shot peening because tooth roots experience repeated bending and can be fatigue-critical. Case condition, root finish, geometry, media access and the complete finishing route determine the result.

Why are shafts and axles shot peened?

Shafts and axles may be peened at fillets, shoulders, splines or transitions that carry cyclic bending or torsion. Bearing, seal and fit surfaces normally need explicit treatment or protection decisions.

Why are springs shot peened?

Springs operate under repeated deflection or torsion, and many spring specifications use shot peening to improve fatigue resistance. Spring material, heat treatment, stress-peening route, coverage and surface quality must be controlled.

Can shot peening improve fatigue resistance?

Yes, when the failure mechanism is surface-related and the material, geometry and process are suitable. The benefit is application-specific and must be supported by the governing specification, qualification or representative testing.

Does every fatigue-critical part benefit from shot peening?

No. Subsurface initiation, an unsuitable material condition, inaccessible geometry, excessive surface damage, a later process step or the wrong failure mechanism can make shot peening ineffective or harmful.

Can carburized parts be shot peened?

Carburized gears and other case-hardened parts are established application families, but the case depth, hardness, retained austenite, grinding condition, roughness and peening parameters must be assessed together.

Can nitrided parts be shot peened?

Selected nitrided parts can be evaluated, but a hard or brittle compound layer, media hardness, sequence, roughness and risk of surface damage require specific qualification. Nitriding plus shot peening does not guarantee an additional fatigue benefit.

What information is needed to evaluate a component?

A drawing, material, heat treatment, critical zone, surface condition, volume and invoked requirements provide a strong start. Include the known failure location or load mode if available; missing parameters can be discussed during feasibility review.

Is shot peening suitable for prototypes?

Yes, prototypes can support access trials, masking development, process-window studies and fatigue validation. A prototype result does not automatically qualify serial production without representative equipment, tooling, controls and approval.

Can SP Center help develop a new shot peening process?

SP Center can review feasibility, masking and tooling concepts, trials, intensity and coverage controls, documentation and qualification planning. The design authority or customer retains approval responsibility unless a contract assigns it differently.

Does the process require customer qualification?

Often, especially for aerospace, automotive, railway, defence and other critical parts. The contract, drawing, specification, approved-source rules and change-control requirements determine the exact route.

How do I know whether my component is a good candidate?

Start with the failure location and load: a surface-initiated fatigue problem at an accessible, highly stressed feature is a stronger candidate than a bulk, thermal or corrosion-driven failure. Send SP Center the drawing and available evidence for a preliminary screening.

Technical review and accountability

Technical content approved by Paweł Kmieć — CEO / SP Center, 2026-08-26.