Lasers promise improved peening

A powerful laser developed at Lawrence Livermore National Laboratory could improve the manufacturing of some airplane components, hip implants, and other metal products. The Lab and Metal Improvement Co. Inc. have signed a license agreement and cooperative research deal to adapt the laser technology to peen, or surface treat, metal. Historically, metals have been peened by bombarding the material with metal balls as small as salt or pepper grains to induce compressive stress that prevents metal fatigue and reduces corrosion. Metal Improvement has found that while conventional peening reaches a depth of about 1/100 of an inch to instill compressive strength, the laser peening method extends some four times deeper. "Laser peening was developed in the 1980s, but never went into production because of high cost and slow lasers," says Jim Daly, senior vice president for Metal Improvement. Livermore's neodymium-doped glass laser achieves 600 watts of average power and is capable of firing 10 pulses per second, compared with one pulse every two seconds from the best commercial lasers. One of the first industries where Daly sees the new laser having an impact is the aviation industry, for peening jet engine components like rotors, disks, blades and shafts. Aviation industry studies have shown that engine blades, which can cost $30,000 to $40,000 apiece, last three to five times longer when treated with the laser peening process. Another plus of the laser peening technique is that it has the potential to increase the resistance of airplane blades to objects like birds, ice, or stones that can damage the edge of a blade. Another use of laser peening beyond safer aircraft could be in the medical industry, for example, in the treatment of the surface of hip joint implants. Other industrial applications foreseen are: oil tools, such as drill collars and mud pumps; marine engines and shafts; rocket engine parts; and the chemical and power-generation industries. Commercial products manufactured with the laser peening process are expected to be two to four years away from introduction. For more information, contact Stephen Wampler, LLNL, at (510) 423-3107.