Laser Shock Peening plus Laser Cladding for Aircraft Landing Gear Repair

Table of Contents

Laser cladding restores the geometry of a damaged landing-gear component. Laser shock peening, applied before and after deposition, modifies the interface and surface through grain refinement and residual compression, compensating for some of the performance loss created by the cladding thermal cycle.

30CrMnSiNi2A Laser cladding Laser shock peening Landing-gear repair

PRE-STRESSGroove LSP

Create a refined layer and residual compression at the future interface.

REBUILDLaser cladding

Fill the damaged region and restore original geometry.

POST-STRESSSurface LSP

Deepen compression and refine the deposited surface.

VERIFYStructure and performance

Inspect fracture, hardness, EBSD, TEM, and bond quality.

First page of a Scientific Reports paper on laser shock peening of laser clad 30CrMnSiNi2A high strength steel — Primary study on the effect of laser shock peening on laser-clad 30CrMnSiNi2A.

Application background

30CrMnSiNi2A is a high-strength steel with useful strength, ductility, and toughness and is used for shafts, connectors, and heavily loaded aircraft landing-gear parts. Local damage and microcracks develop during service.

Laser cladding (LC) rebuilds lost geometry, but its thermal cycle introduces stress and may reduce mechanical performance. Laser shock peening (LSP) creates residual compressive stress and grain refinement. Combining the two provides a route to dimensional and mechanical restoration.

The study compares two routes:

Route 1LSP + LC + LSP

Shock-peen the repair groove, deposit the clad, then peen the surface.

Route 2LC + LSP

Deposit without groove pretreatment and peen only the finished surface.

The comparison isolates the contribution of groove pretreatment to interface quality.

Laser shock peening with absorbing layer confining layer high pressure plasma and shock wave — A short pulse forms high-pressure plasma in an absorbing layer; confinement directs the shock into the workpiece.

Plastic strain and residual compressive stress induced below a laser shock peened surface — Plastic strain produces residual compression in the surface and subsurface.

Experimental parameters

Material and process

The substrate and powder are both 30CrMnSiNi2A. Principal composition ranges are C 0.27–0.34%, Cr 0.9–1.2%, and Ni 1.4–1.8%.

Laser-cladding parameters

power: 0.8 kW
travel speed: 8 mm/s
overlap: 50%
shielding: Ar

Laser-shock-peening parameters

groove LSP: 2 J, 2 mm spot, 3.18 GW/cm²
surface LSP: 3 J, 2.2 mm spot, 3.95 GW/cm², using higher energy for a deeper stress field

Laser cladding laser shock peening and mechanical test specimen arrangement — Specimens for cladding, peening, and mechanical testing.

Transverse and longitudinal sampling positions for microstructure testing — Transverse and longitudinal sampling locations.

EBSD and TEM sampling locations in laser clad and shock peened specimens — EBSD and TEM sampling locations.

Core innovation: groove LSP and surface LSP

Why shock-peen the groove?

The groove becomes the clad–substrate interface, where conventional LC can leave microcracks under thermal stress. A 2 J groove treatment at 3.18 GW/cm² produces high dislocation density, grain refinement, and residual compression. During deposition, the pre-existing compressive state offsets part of the tensile thermal stress and improves interface strength.

The lower groove energy avoids excessive distortion that would reduce dimensional accuracy before deposition.

Surface LSP after cladding

A 3 J, 3.95 GW/cm² surface treatment serves two purposes:

the residual-compression layer can extend beyond 1 mm, compared with approximately 0.2–0.5 mm for conventional shot peening;
columnar austenite grains approximately 30–40 µm are refined into 4–8 µm equiaxed grains, dislocation density rises, and hardness reaches approximately 800 HV₀.₂.

With and without groove pretreatment

Without groove LSP, the clad–substrate interface remains the weak location and the fracture surface contains more pores. The groove-LSP specimen has a denser fracture and dimples closer to those of the substrate, indicating better bonding and ductile response.

Tensile fracture surface of a laser clad and surface shock peened sample — Fracture after LC plus surface LSP.

Tensile fracture surface after groove shock peening laser cladding and surface shock peening — Fracture after groove LSP, LC, and surface LSP.

SEM of laser clad regions with and without LSP and the clad heat affected zone interface — SEM overview, peened and unpeened regions, and the clad–HAZ interface.

EBSD grain morphology orientation and distribution in laser clad and shock peened specimens — EBSD comparison of grain morphology, orientation, and distribution.

TEM showing deformation twins dislocation tangles and lath martensite in peened and untreated regions — TEM of peened material, deformation twins, dislocation tangles, lath martensite, and untreated material.

Reproduction workflow

Step 1: substrate preparation

Machine a trapezoidal groove to match the damage depth, grind to Ra < 1.6 µm, and degrease with acetone.

Apply groove LSP at 2 J per pulse with 50% spot overlap. A single-spot trial should confirm that the surface does not ablate before full-area processing.

Step 2: laser cladding

Vacuum-dry powder at 100–110 °C for approximately one hour, especially in humid environments.
After each layer, forced-air cool toward 150–200 °C to limit heat accumulation and excessive austenite coarsening.

Step 3: surface LSP

Begin with a 3 J single-pulse trial and measure the hardness gradient. Increase energy if the required hardness is not reached at 1 mm depth.
Verify continuous coverage metallographically and adjust overlap if untreated gaps remain.

Engineering considerations

The “peen the groove, rebuild, then peen the surface” strategy addresses both interface and surface performance, but practical use has three constraints:

Equipment cost: the study uses separate IPG YLS-2000 cladding and Nd:YAG peening systems.
Geometric adaptability: uneven clad thickness changes effective peening depth, while curved surfaces make coverage and incidence harder to control.
High-temperature stability: refined grains and dislocation structures may recover during service and reduce the strengthening effect.

The method is therefore best suited to high-value, low-volume repair where performance improvement justifies complex equipment and qualification.

References

Wang, L., Yu, K., Cheng, X. et al. “Effect of Laser Shock Peening on Microstructure and Mechanical Properties of Laser Cladding 30CrMnSiNi2A High-Strength Steel.” Scientific Reports 13, 9971 (2023). DOI: 10.1038/s41598-023-37060-w.
Cao, X.; Wu, J.; Zhong, G.; Wu, J.; Chen, X. “Laser Shock Peening: Fundamentals and Mechanisms of Metallic Material Wear Resistance Improvement.” Materials 17 (2024), 909. DOI: 10.3390/ma17040909.

The original Chinese edition was published by “Laser Insights” in Chongqing on March 10, 2025. View the original post. This page preserves the complete technical content, parameters, figures, conclusions, and references.