Fiber Laser Micro-machining of Ti-6Al-4V

Progress of laser micro-machining i.e. micro-cutting, micro-drilling, Micro-channeling, micro-grooving, micro-turning etc. in the field of aeronautic, automobile, semiconductor and biomedical industries such as turbine blades of aircraft engine, automotive fuel filters, combustion chambers, surgical needles and micro-fluidic devices have emerged extensively in the present era. The prime contributor to the success of laser micro-machining in the recent years is fiber laser technology that involves the combination of diode pumped solid state lasers and fiber technology. This is the most promising substitute to the high-power, bulk solid-state lasers and some gas lasers owing to its simplicity, ruggedness, cost effectiveness, low maintenance, higher efficiency, higher reliability and smaller spot size. Fiber lasers are mainly characterized by short pulse lengths which range from millisecond to picosecond and even femtosecond for precise micro-machining of different materials. Titanium alloys play crucial roles in the areas of advanced structures and technologies for aerospace and power industry, medicine, automatics and mechatronics and various measurement equipments, because of their high strength and stiffness at elevated temperatures, high corrosion resistance, fatigue resistance, high strength to weight ratio and ability to withstand moderately high temperatures without creeping. The conventional machining methods intended for cutting these alloys not only suffer due to poor thermal conductivity, low elastic modulus and high chemical affinity at elevated temperatures but also have to undergo higher cost associated with the machining of Ti-6Al-4V caused by lower cutting speeds and shorter tool life. Numerous research works have been conducted with laser beam micro-machining approaches on titanium alloys mainly on Ti-6Al-4V, in order to establish the optimal experimental conditions that are to be used in different applications. However, the physical mechanism which leads to the observed geometry and surface roughness of the micro-machined surface is still behind the veil. The aim of the present chapter is to make an in depth study of the fiber laser micro-grooving of Ti-6Al-4V, discussing vividly the fiber laser machining system, the occurring physical processes and machining strategy and influence of various process parameters. Experimental results of present research work along with the work of various researchers are discussed so as to validate and run down hypotheses on the mechanisms involved.