Experimental and Parametric Evaluation of Quality Characteristics in Nd:YAG Laser Micro-Drilling of Ti6Al4V and AISI 316

Abstract

Titanium alloy of grade-5 (Ti6Al4V) and stainless steel of grade AISI 316 have wide applications in various engineering sectors due to their favorable material properties such as low thermal conductivity, high corrosion resistance and high strength to weight ratio. The literature survey suggests that Ti6Al4V and AISI 316 have the similar field of applications and comparative study of both the materials was limited. In the present study, laser drilling of Ti6Al4V and AISI 316 have been performed using Nd:YAG millisecond laser under identical machining conditions. The control parameters considered for the study are laser energy, pulse repetition rate, pulse width and flushing pressure having each at three different levels. To reduce the total number of experimental run and obtain maximum information for the experimental trials, Taguchi’s L27 orthogonal array has been adopted. Further, the study has been focused to understand the behavior based on experimental data on similarities and differences between laser drilling process of Ti6Al4V and AISI 316 are qualitative. The outcome of experiments in terms of circularity of hole and heat affected zone (HAZ) for laser drilled holes are studied. It is observed that HAZ increases with increase in laser energy and pulse repetition rate. It may be due to a higher average power of the laser beam, which is directly proportional to laser energy and pulse repetition rate. Higher the value of laser energy, higher will be the laser thermal energy and higher HAZ. Heat affected zone (HAZ) can be minimized with low laser energy and pulse width during laser drilling of Ti6Al4V and AISI 316. From the study, it is revealed that pulse repetition rate is the most significant parameter in the formation of circularity and HAZ.