Effect of laser welding parameters on characteristics, microstructure and microhardness of Inconel 718 superalloy- AISI 321 stainless steel joint

This research investigated the dissimilar welding process of Inconel 718 superalloy alloy to AISI 321 stainless steel by Nd: YAG laser welding without the use of any filler metal. The welding parameters, microstructures and microhardness of the joints were also studied. For this purpose, the microstructures of the welded specimens were examined using an optical microscope and a scanning electron microscope. The results showed that all the joints were well-formed and there was no discontinuity, gas porosity, cavity and impurity at the joint location. Among the specimens that had good welding conditions in appearance, depth of penetration, and weld width, specimen B3 with the maximum energy input (47.44 J/mm), specimen B2 with an average energy of 36 J/mm and specimen C3 with an average energy of 37.6 J/mm were evaluated. The average size of solidification grains in these three specimens were 93, 66 and 59 μm, respectively. It was also observed that there was a similar trend in hardness changes in all three specimens. From the base metal towards the weld metal, first there was a decrease and then a steady increase in the hardness of the weld metal was observed. The hardness value in the specimen with a higher amount of energy input (B3) decreased significantly compared with those of the other two specimens.

Keywords:

Inconel 718 , AISI 321 stainless steel , laser welding , welding speed , pulse width , microhardness