Laser Transformation Hardening of Unalloyed Titanium Using Nd: YAG laser

This paper presents the results of Laser surface Transformation Hardening (LSTH) of unalloyed Titanium sheet with chemical composition nearer to ASTM Gr.3 material. LSTH is carried out on a 1.6mm sheet surface with varying the beam parameters such as beam power, spot size and welding speed. The beam is defocused at three levels, i.e. +10, +20 and +30mm. Overlapping of subsequent scanning is kept constant at 25%. Focal length and shielding gas flow rate is set at 120mm and 8lpm respectively. The experiments are carried out using a 2kW CW solid state Nd:YAG laser source. The laser scanned sheet cross section is analyzed to study the effect of above mentioned laser beam parameters on the responses such as width and depth of laser hardened layer. Study indicates a maximum width of 3mm hardened area per scan and hardness depth up to 0.7mm using the selected parameters. Laser hardened cross section is analyzed for hardness and its micro structural properties. As against the base material hardness of around 150HV minimum, laser hardened area reached hardness around 245HV maximum. Microanalysis showed no damage in the interface and a flawless transition between hardened and base material zones.