Dispelling Four Myths About Laser Shock Peening
Laser Peening is not just a variation on shot peening -- it's more precise and powerful
Posted: May 15, 2018
Laser shock peening (LSP) is a powerful process for enhancing metal parts. Laser peening improves metal fatigue resistance, enabling OEMs and their customers to get more out of high-value components. LSP has been around for decades, yet there are still plenty of myths and misunderstandings surrounding this surface enhancement solution.
Myth #1: Laser peening is just a high-tech version of shot peening.
Many people still erroneously equate laser peening with shot peening, but these applications remain worlds apart in both their capabilities and results.
Shot peening bombards a metal surface with little pellets or balls. Laser peening uses high-energy light pulses to generate powerful plasma explosions. Do those two processes sound at all like the same thing?
Imagine I gave you two options: Catch a fastball from a professional baseball pitcher or catch a burning stick of dynamite. It’s no contest, right? A 100-mph fastball will make your hand sting, but a LITERAL EXPLOSION will remove that hand altogether.
This gives you a sense of the magnitude discrepancy between these surface enhancement treatments. Shot peening is archaic, shallow, and imprecise. Laser peening is deep, powerful, and cutting-edge.
There are countless advantages to laser peening over shot peening, but the biggest difference simply comes down to results: Laser peening generates deeper compressive stress for longer lasting parts. In some cases, the residual stress depth and part life extensions surpass shot peening by an order of magnitude.
There really is no comparison. And yet the myth persists – possibly perpetuated by shot peening providers? Some even refer to laser peening as “Laser Shot Peening”, which is a woeful misnomer akin to calling your 3D printer a “Laser Forge”.
Myth #2: Laser peening is a thermal process
When most people think of industrial lasers, they typically picture welding, cutting, or drilling. These processes use the laser beam as a concentrated heat source to melt or remove material, relying mainly on thermal energy to do the work. Lasers are great for these applications because they deliver carefully calibrated energy with high precision. A laser can apply intense heat to a targeted area while leaving the surrounding material relatively unaffected.
Laser peening operates on a slightly different principle. For one, it’s a pulsed laser application, meaning the energy is delivered in short pulses rather than a continuous beam. Each pulse lasts just a few billionths of a second, and the thermal load transferred to the metal is limited. These short, concentrated pulses generate plasma bursts on the part surface, and that plasma powers a mechanical shockwave which does the work in the part.
Laser peening is all about that shockwave. (That’s why it’s called laser shock peening.) The shockwave energy propagates into the material producing compressive residual stress. The more powerful the shockwave, the deeper and more robust the compressive stress. The energy in the shockwave isn’t derived from the heat of the laser, but rather the pressure generated by rapidly expanding plasma on the metal surface.
Laser peening is a means of turning light energy into mechanical work.
Myth #3: Laser peening is only for aerospace
Laser peening was born out of a need for superior cracking prevention in aircraft engine components. It was first adopted by the U.S. Air Force and major engine manufacturers. This was a natural fit as aircraft engine blades operate at high performance thresholds and have high consequences of failure.
After demonstrating major benefits in aerospace, LSP adoption quickly spread to gas turbine manufacturing for the power generation industry. Laser peening was shown to reduce costly inspection and maintenance requirements, and the nuclear industry also developed LSP applications to extend the service life of critical infrastructure.
Each successive year has brought new industries and applications into the fold as manufacturers seek superior enhancement to get more life out of components. Laser peening is as versatile as it is powerful, making it a veritable Swiss army knife for metal enhancement applications.
A few key points:
- Laser peening works on all metals, with a wide range of power densities and application patterns to enhance any surface.
- Laser peening is a precision application that delivers targeted enhancement where components need it most.
- Laser peening applications can be reliably modeled to optimize process parameters before a single pulse is fired.
The potential applications for laser peening are limited only by our willingness to explore them. Aerospace and power gen manufacturers were early adopters because the benefits were clear on their high-value equipment. Now, as laser peening production costs continue to decrease, a whole host of new industries can get in on the savings as we dispel our final myth…
Myth #4: Laser peening is too expensive
It’s easy to understand what’s contributed to this myth. Laser peening sounds high-tech, sophisticated, and presumably expensive. However recent innovations have led to significant declines in production costs, and the ROI associated with component life extension pays for itself many times over.
In the early days, laser peening equipment was fairly costly and slow. First-generation systems delivered one pulse every few seconds, limiting production throughput and keeping costs high.
Fast-forward to today, and everything has changed. Laser peening processing rates have improved many times over, and the knowledge around LSP applications is growing by leaps and bounds.
A major factor has been advancements in laser technology, and the move from flashlamp pumped laser systems to those powered by diodes. Diode-pumped systems are vastly more efficient and can speed up processing rates by a factor of ten.
LSP Technologies’ diode-pumped Procudo® Laser Peening System operates at speeds up to 20 Hz. This substantial improvement in production throughput lowers the cost of processing each part. Automation solutions and advancements in robotics allow for seamless automated part-handling, and the growing knowledge base around LSP is accelerating application development and qualification.
All this adds up to cheaper production costs that are making laser peening accessible to new industries. Meanwhile, the cost savings associated with component life extension, failure prevention, and reduced maintenance requirements provide a clear return on investment that is unmatched by other surface treatment applications.
The bottom line: this ain’t your granddad’s laser peening. Today’s equipment is faster, more efficient, and optimized for high-volume production processing. Laser peening can deliver a 10X improvement on shot peening and the ROI speaks for itself.
Don’t believe the myths.
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