Ultrafast drilling of turbine cooling holes trades speed for a missing recast layer
Percussion drilling with millisecond pulses is fast and leaves a damaged layer. Ultrafast drilling is slow and does not, which matters for fatigue life.
A turbine blade carries hundreds of small cooling holes through which air is bled to form a protective film. Drilling them is a well-established laser application, and the process choice illustrates a recurring ultrafast trade-off precisely.
What conventional drilling leaves behind
Percussion and trepanning with millisecond or microsecond pulses melt material and expel it. Some melt resolidifies on the hole wall as a recast layer, typically with microcracks, and beneath it lies a heat-affected zone with altered microstructure.
On a component that operates at high temperature under cyclic load, that layer is a crack initiation site. Aerospace specifications limit recast thickness, and removal by chemical or mechanical means is an additional process step with its own tolerance implications.
What ultrafast changes
Femtosecond and picosecond pulses remove material by ablation with minimal melting. The hole wall shows little or no recast and a negligible heat-affected zone, which removes both the fatigue concern and the downstream removal step.
For holes through thermal barrier coatings, ultrafast also avoids the coating delamination that melt-based drilling can cause at the interface.
The cost
Speed. Ablation removes material in far smaller increments, so drilling a hole takes considerably longer. On a component with hundreds of holes, that difference is measured in hours per part.
Equipment cost is higher and the service ecosystem thinner.
Where each wins
Components where recast is acceptable, or where a removal step is already in the process, continue to use conventional drilling on throughput grounds. Components where fatigue margin is critical, where the geometry makes recast removal impractical, or where coatings complicate melt-based approaches, justify ultrafast.
Hybrid approaches exist: conventional drilling for the bulk of the hole followed by ultrafast finishing of the wall, capturing most of the speed with most of the quality.
The general pattern
This is the same trade that appears across ultrafast applications. The process is not better in general; it is better where the thermal damage of a faster process is the limiting factor. Where it is not, the speed penalty is simply a penalty — and identifying which case applies is the engineering judgement the technology demands.
This article was produced by the LasersNews AI desk and reviewed by our editors.
Related reading
Ultrafast lasers solved the quality problem. Throughput is the remaining one
Beam splitting, polygon scanning and higher repetition rates are the levers turning femtosecond precision int…
"Cold ablation" is a useful simplification that hides where the heat goes
Femtosecond pulses remove material before heat diffuses. Repeat them at high rates and heat accumulates anywa…
Filamentation cutting made thin glass a manufacturable material
Self-focusing inside the glass creates a column of modified material through the full thickness. The glass th…