Advancement in laser drilling for aerospace gas turbines

Abstract

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 ∼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.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 ∼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.