Experimental Investigation of the Metallurgical and Mechanical Properties of a Nd: YAG Laser-Welded Inconel-825 Superalloy

Inconel-825 is a nickel-based superalloy that can maintain its properties at high elevated temperatures up to 1550 °C. It is primarily used in applications such as Rocket engines, Gas turbine blades and nuclear reactors. In this research paper Inconel-825 pieces with 2 mm thickness are welded by Nd:YAG laser welding having laser power of 3 kW by varying power (70%, 65%, 60%, 55% and 50%) and a total of 5 experiments are carried out. The quality of the weld is investigated by mechanical tests such as a computer-assisted universal testing machine, and the hardness number is identified by using the Vickers hardness test on the fusion zone. Metallurgical investigation was carried out by optical microscopy to identify equiaxed grain growth in the fusion zone. The results reveal that by utilizing a laser power of 50%, i.e., 1.5 kW, the mechanical and metallurgical properties are improved; the UTS is 538 MPa, the % elongation is 16.50%, the hardness is 220.75 BHN, and the average grain size is 2.90 µm. Fine grains are formed and ductility is improved in the fusion zone. Still improving the power to 65% i.e. 1.95 kW, coarse grains are formed such that brittleness is improved, and the SEM morphology revealed that high power welding of Inconel-825 cooling takes place in a rapid manner, leading to internal crack generation in the weld zone and a further reduction in weld strength.