Advanced Balancing Using Laser Machining

The development of a pilot production, automated laser balancing system and the results of metallurgical evaluations of laser machined materials are presented in this paper. The automated laser balancing system is designed to low speed balance, small gas turbine engine components, such as AGT1500 compressors, turbines and shafts in a single load and spin-up cycle. A high power pulsed Nd:YAG laser is used to remove material from components while they rotate at speeds to 2,000 RPM for increased balance precision and efficiency. Metallurgical examinations of laser affected zones in turbine engine materials such as 17-22A(s), IN718, AM355, Waspaloy and IN713LC as well as material fatigue testing are presently being conducted to assess the effects of the laser material removal process on both material and component fatigue life. This paper, however, presents a summary of only the 17-22A(s) results. Specimens representing manual handground balanced and as-machined new components were also prepared and fatigue tested for comparison with the laser machined specimens. Preliminary results indicate that both the hand grinding and laser machining degrade material fatigue strength. Laser machining does appear to degrade material fatigue life to a greater extent than handgrinding. However, when comparing the material fatigue life to the required life for a 17-22A(s) component, the laser machined material does retain adequate life for that component. Efforts are underway to develop laser machining processing approaches which do not degrade component life for AM355, Waspaloy, IN718, and IN713LC materials.