Abstract
The paper deals with the evaluation of the shielding gas influence on the properties of titanium Grade 2 weld joints produced with disk laser. Butt weld joints were produced under different shielding gas types, namely Ar, He, Ar + 5 vol.% He, Ar + 30 vol.% He, and without shielding weld pool. Light and electron microscopy, microhardness measurements, computed tomography, and tensile testing were used for evaluation of weld joint properties. He-shielded weld joints were the narrowest ones.
On the other hand, Ar shielded weld joints exhibited the largest weld width. The choice of shielding gas had a significant influence on the porosity of welds. The lowest porosity was observed in the weld joint produced in Ar with the addition of 30 vol.% He shielding atmosphere (only 0.03 %), while the highest level of porosity was detected in weld joint produced without shielding gas (0.76 %). Except for unshielded titanium Grade 2 weld joint, the lowest tensile strength was recorded in Ar-shielded weld joints. On the contrary, the highest average microhardness, except unshielded weld joint, was measured in He-shielded weld joints.

Key words
disk laser, laser welding, commercially pure titanium Grade 2, shielding gas, porosity

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