Laser drilling assisted with jet electrochemical machining for the minimization of recast and spatter

Abstract

Laser drilling is increasingly becoming the method of choice for precision drilling for a variety of components. The most important application is the drilling of fine cooling holes in aero turbine engine components such as nozzle guide vanes and blades. However, a number of defects such as recast, spatter and heat-affected zone limit the application. The elimination of these defects is the subject of intense research. This paper presents a novel hybrid process of laser drilling assisted with jet electrochemical machining (JECM-LD) which can minimize the recast and spatter. The process is based on the application of a jet electrolyte, being aligned coaxially with the focused laser beam, on the workpiece surface. The effects of the jet electrolyte during the process mostly consist of electrochemical reaction, effective cooling with materials and transporting debris. JECM-LD experiments were performed on 0.5-mm thickness 321 stainless steel with pulsed Nd:YAG laser at second harmonic wavelength. The optical microscope and scanning electron microscope were used to detect the experimental results. It is found that the spatter has been reduced more than 95%, and recast has been reduced more than 90% during the JECM-LD compared with laser drilling in ambient atmosphere conditions.