Microforatura laser di titanio: Studio del processo e valutazione del suo effetto sulla microstruttura del materiale --- Laser microdrilling of titanium: Investigation of the process and evaluation of its effect on material microstructure|

Laser micromachining are becoming a relevant topic in industrial applications, mainly thanks to the continuos evolution of the laser sources. The thermal damages on the material, after to be laser processed, is a fundamental aspect as a result of the machining. For this reason, laser sources, which are able to minimize the heat introduced inside the workpiece during the process, are considered very suitable for their applications in industrial cases. In this context the introduction of pulsed fiber lasers, which are applied to perform material microprocessing, have to be put in evidence. These are innovative laser sources, which are very interesting to be applied for high precision machining of small features, thanks to their positive characteristics, such as high beam quality, high focusability, high productivity and reliability. Consequently, the study and the evaluation of their performances in material microprocessing can be considered as a relevant topic of the last years for both academic and industrial researches. In this work a study on laser percussion microdrilling on 0.5 mm thick commercially-pure titanium sheets with a nanosecond pulsed fiber laser was investigated. The work was aimed at investigating the effect of the main process parameters (pulse energy and pulse frequency) on the quality features of the machined through holes (mean diameters, aspects and area of top spatter) and at evaluating the effects of laser machining on material microstructure by means of nanohardness measurements around the machined holes. Regressive models of the investigated hole quality features and the dimension of the thermal affected zone were proposed. Besides cross sections of the holes performed in two process conditions were considered in order to evaluate the inner shape of the holes and the thermal effect of the laser micromachining process.