Aerospace gas turbines require a large number of small diameter holes (<1mm) to provide cooling in the turbine blades, nozzle guide vanes, combustion chambers and afterburner. Many thousands of holes are introduced in the surface of these components to allow a film of cooling air to flow over the component. Film cooling both extends the life of the component and enables extra performance to be achieved from the engine. A typical modern engine will have approx 100,000 such holes. Drilling these cooling holes by high peak power pulsed Nd-YAG laser is now well established. Such holes can be successfully produced by laser trepanning or percussion drilling. This paper investigates laser percussion drilling with a high peak power pulsed Nd: YAG laser (up to 20kW) using both direct beam delivery and fiber delivered systems. A number of holes were drilled with different laser and processing parameters on nickel based superalloy to quantify laser drilling times, recast layer, taper, oxidized layer and cracking.
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