The World’s Most Powerful Surface Enhancement Technology
Laser peening is a fascinating marriage of electromagnetic physics and materials science. The process uses high-energy lasers to strengthen metals, producing robust components that are highly resistant to failure. Laser peening (LSP for short) plays a critical role enhancing critical parts for critical industries. You’ll find laser peened parts in aircraft engines, power plants, and heavy machinery around the world.
If you’re new to the world of laser peening, we’ve got a wealth of technical content available at your fingertips. (Check out our library of papers and patents!) But before taking that deep dive, here are five interesting facts to put this revolutionary enhancement process in perspective.
1) Light Can Strengthen Steel
It’s worth taking a step back to consider the awesome implications of peening metal with lasers. We’re using pulses of light to strengthen steel and titanium, replacing old-world peening techniques with new-age technology.
Metal enhancement has come a long way
It used to be done with hammers. The rounded head of a ball peen has long been used by blacksmiths to pound and shape forged components. These brute-force blows put compressive stresses into tools and armor, but their enhancement benefits weren’t fully realized until the 1920s when a budding auto industry adopted shot peening to strengthen springs.
Shot peening is another brute-force enhancement method using high-velocity impacts to generate compressive stress. The process requires thousands of pellets or particles, launched toward a workpiece to produce a thin accumulation of surface compression. It’s messy and imprecise, and the benefits extend just fractions of a millimeter beneath the surface.
Laser peening transcends the old barrage-based methods, taking surface enhancement to another level. Coherent photon pulses impart compressive stresses many times deeper than hammers or shot pellets could ever achieve. With all due respect to the burly blacksmiths of the world, laser peening has moved metal enhancement out of the dark ages with blasts of light.
2) Plasma Does the Work
Laser shock peening is the next generation of material improvement. This powerful surface enhancement process improves metal fatigue strength up to twenty times – providing invaluable service life extensions for critical components. Though traditionally applied to steels, titanium, and other metals, laser peening is now proving a valuable application for a new class of material: engineered ceramics.
The NASA Space Shuttle incorporated ceramic tiles for high heat resistance
Ceramic engineering involves manufacturing objects from inorganic, non-metallic materials like silicon or zirconia. Ceramic parts offer several key advantages over their metal components in that they are lighter, noncorrosive, and offer superior heat resistance.
Ceramics in Aerospace
Ceramic materials have been used in targeted aerospace applications for years, providing thermal protection and insulation for the Space Shuttle to withstand the extreme temperatures of atmospheric reentry. As ceramic engineering has evolved, these versatile materials have been employed in applications ranging from brake pads to ball bearings to bulletproof vests. Continue reading
Beneficial Compressive Residual Stresses
Fatigue strength improvements are proportional to the magnitude and depth of induced compressive residual stresses present in a component. Deeper compressive residual stresses provide superior resistance to crack propagation and fatigue failure. Laser peening typically produces compressive residual stresses up to 10X deeper than competing surface enhancement processes.
So how does laser peening produce effective compressive residual stress profiles? LSPT engineers control the depth and magnitude of compressive residual stresses by increasing the power density and coverage of the laser pulse.
Compared to shot peening, laser peened parts retain deeper compressive residual stress profiles in high-temperature environments. Laser peening’s superior heat resistance results from the lower percentage of cold work involved, producing deep compressive residual stresses that remain stable at elevated temperatures.
Surface enhancement techniques like shot peening and laser peening rely upon plastic strain to produce beneficial compressive residual stresses within a material. Laser peening is a mechanical process that utilizes a high-energy, pulsed laser to generate a compressive stress wave at the surface of a part. The compressive stress wave induces plastic deformation as it propagates into the material, causing dislocations in the microstructure that enhance the strength and fatigue resistance of the part. Compressive residual stresses inhibit the initiation and propagation of fatigue cracks.
Metal Fatigue Prevention
Metal fatigue failure typically results from microscopic crack formation at the surface of the material. Cracks may initiate due to cyclic loading, foreign object damage, or corrosive environments, and cracks will propagate with successive loads or continued exposure until failure occurs.
Enhancing materials through the introduction of compressive residual stresses inhibits the initiation and propagation of fatigue cracks. Compressive residual stresses provide a counterbalance to the tensile stresses present at the part surface, and the compressive environment slows the propagation of microcracks. Deep compressive residual stresses provide enhanced fatigue resistance, and can significantly extend the fatigue life of a metal part.