Experimental investigation of the metallurgical and mechanical properties of laser weld Inconel 825 joints for petrochemical plants

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 petrochemical industry. In this research paper, Inconel-825 with a 2 mm thickness was welded via Nd:YAG laser welding with a laser power of 3 kW by varying the power (70%, 65%, 60%, 55% and 50%). 5 experiments were carried out, the mechanical and metallurgical properties improve the UTS to 538 MPa, the elongation was 16.50%, the hardness in the fusion zone was 221 hV, and the average grain size is 2.90 µm, indicating the formation of fine grain microstructure which contributed to improved mechanical strength. As the laser power increased to 65%, i.e. 1.95 kW, the weld exhibited a grain size of 12.91 µm indicating the coarse grain formation in the fusion zone leading to increased brittleness and the elongation dropping to 2.00%, the corresponding hardness was 167 hV and the SEM micrographs revealed that high-power welding, leading to increase in grain size correlated with a increase in brittleness. EDS analysis confirmed the presence of Al2O3 at power-1.5 kW level associated with bonding strength. At power-1.95 kW and 2NiO was detected which facilitated the formation of internal cracks and significant decline in weld quality.