Laser Peening

Laser peening induces exceptionally deep residual compressive stresses which enhance the fatigue strength and durability of critical metallic components.
Laser peening is not a replacement for controlled shot peening, but has additional advantages that can influence which method to use.

Laser peening is making an important impact on industry as a reliable and production qualified technology. Laser peening offers designers the ability to surgically place residual compressive stress into key areas of components to retard crack initiation and growth enabling increased fatigue strength and component lifetime.

Benefits of laser shock peening

  • Deeper residual compressive stress enabling better resistance to:
    • Low cycle, high stress situations (LCF)
    • High cycle, low stress situations (HCF) in a deteriorating surface environment
    • Erosion, strike damage, fretting and corrosion
  • Less cold work enables greater retention of residual compressive stress in high load and/or thermally challenging conditions
  • Lack of shot particles using “clean” technology enables applications where contamination and/or media staining cannot be tolerated.
  • Original surface finish and topography easily maintained and controlled
  • Allows for excellent process and quality control

Applications for laser peening

Laser shock Peening is been used to prolong the fatigue life of critical aerospace components such as turbine engines and aircraft structures as well as for wing skins to achieve the requirements of the new generation of intercontinental aircraft.

Laser shock peen forming essentially performs the same role as Peen Forming, but because of the greater depth of plastic work, extends the degree of curvatures possible enabling more fuel efficient profiles to be achieved.

Potential applications of laser shock peen forming have also emerged for automotive, power generation, nuclear waste disposal, drilling, medical implants and recreational sports.

Laser peening process

An output beam, roughly 25 Joules at 18 nanoseconds from a Nd:glass laser is projected onto a work piece to induce a residual compressive stress. The area to be peened can be covered with material to act as an ablative layer and simultaneously as a thermal insulating layer, or peened directly onto the base metal which subsequently may require some form of surface removal of a few microns.

Laser Peening

A thin stream of water is made to flow over the surface, the laser light transparently passes through the water and the leading temporal edge of the laser pulse is absorbed on the metal surface or ablative layer. This absorption rapidly ionizes and vaporizes more of the surface material to rapidly form a plasma that is highly absorbing for the rest of the laser pulse.

A high plasma builds to approximately 100kBar (1 million pounds per square inch) with the water serving to inertially confine the pressure. This rapid rise in pressure effectively creates a shock wave that penetrates into the metal, plastically straining the near surface layer.

The plastic strain results in a residual compressive stress that penetrates to a depth of between 1mm and 8mm depending on the material and the processing conditions. This deep level of compressive stress creates a damage tolerant layer and a barrier to crack initiation and growth, which consequently enhances the fatigue lifetime and provides resistance to stress corrosion cracking and fretting fatigue.

Laser peening of AI 6061-T6

Multiple firings of the laser in a pre-defined surface pattern will impart a layer of plastic strain resulting in a deep layer of compressive residual stress. The process can be tailored to suit the product and potential failure mechanism or enable higher potential loads through weight sensitive designs.

One benefit of an exceptionally deep residual compressive layer is shown above. The S-N curve shows fatigue test results of 6061-T6 aluminum. The testing consisted of unpeened, shot peened and laser peened specimens.

Laser PeeningMobile Laser Peening

Our mobile Laser Peening Facility enables application of the laser peening technology at the customer’s site.

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