Investigation of weldability of titanium alloys with different welding methods

In this study, 2.5 mm of thickness commercially pure titanium sheets (Cp-Ti) were welded by laser welding and TIG welding methods. The mechanical properties of titanium sheets which were welded by different welding methods were investigated. TIG welding was carried out double sided and one pass by using ERTi-2 filler rod in 80A, 220V with DC voltage of positive polarity. Laser welding was carried out double sided without using filler rod, in 5 ms pulse duration, 30 Hz repetition rate and 270 W average power with a pulsed Nd:YAG laser. In both welding methods, Ar shielding gas were used.According to the TS-5789, tensile and bending test specimens were obtained from welded sheets. The results were compared with the values of the main material by applying tensile and bending tests to the laser welded and the TIG welded specimens. As a result of the tensile and bending tests, it was specified that the strength of the main material was the highest; the strength of laser welded specimens had higher values than TIG welded specimens. All specimens fractured from main material part. By using Vickers Hardness measurements, it is determined the hardness variation caused by temperature changes during the welding operations of commercially pure titanium sheets. The hardness of main material was nearly 190-200 HV, in the weld zone of the laser welded specimens was 280-300 HV but in the weld zone of the TIG welded specimens was higher than 400 HV. In order to determine the microstructural changes of the specimens optical microscope and SEM analysis were performed from weld zone to base metal.As a result of mechanical tests and metallographic investigations if we want to use the welded commercially pure titanium (Grade-2) in constructions it is determined that laser welding is the most suitable welding method.