A study on film hole drilling of IN718 superalloy via laser machining combined with high temperature chemical etching

A novel method of laser machining combined with high temperature chemical etching (LMHTCE) was proposed. This novel method can take full advantage of both approaches to drill film holes in an IN718 superalloy without a recast layer or a heat affect zone (HAZ). A solution of hydrochloric acid and sodium nitrate, which minimally reacts with IN718 at room temperature but rapidly reacts under high temperatures, was tested and chosen. Holes drilled in air, water, and chemical solutions by a pulsed laser of 1064 nm were studied, and scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were employed to detect the morphology of the holes and the elemental distribution in different zones. The holes processed in the chemical solution had fewer defects compared with those in the other two mediums. The defocusing distance parameter was optimized to minimize the hole diameter and taper. When the defocusing distance was 0 μm in the drilling stage and − 60 μm in the high temperature chemical etching stage, a hole with a smaller diameter and taper can be obtained.