Experimental study on weld formation of Inconel 718 with fiber laser welding under reduced ambient pressure

A 10 kW fiber laser was used to join 10-mm-thick Inconel 718 alloy plates. Humping, porosities and splash occurred during laser welding under atmosphere pressure. Laser welding under reduced ambient pressure could be beneficial for improving the weld formation and penetration depth. The experimental results showed that weld appearance became smooth and bright with the decrease of ambient pressure. A penetrated welding joint without defects was obtained when the ambient pressure was 4 × 10−3 Pa. Distribution of plasma showed that the plasma area decreased due to the less mutual collision frequency between particles under lower ambient pressure. Smaller area of plasma resulted in a higher laser energy absorption efficiency, which finally led to a deeper penetration. The computational results indicated that the boiling points of these alloying elements decreased sharply when the ambient pressure reduced. Lower boiling points of these alloying elements helps to form a more stable molten pool, which finally led to the satisfactory weld formation.