## 1 Introduction
It was also observed that the hardness decreases at the bottom of the blocks due to progressive re-heating. Furthermore, [PERSON] and [PERSON] [12] attempted to eliminate the directional limits of robotic WAAM by developing a multidirectional WAAM process. This experiment was justified by the fabrication of a workpiece with overhangs. The torch angle was maintained vertically while the travel speed was selected according to the stability required for the deposition of vertical walls 1 and 2. The results show that the manufacturing time decreased by 52%, material cost by 57% and material usage by 57%. The parabola bead model helped to obtain the desired bead geometry, while the multi-direction strategy was used by decomposing a CAD model into a sub volume along with the desired build directions. Because of low heat input and short arc transfer behaviour, CMT was preferred for welding deposition. It has also been emphasized that the buY-to-fly ratio plays a vital role in multidirectional WAAM applications. Recently, [PERSON] et al. [16] attempted to determine the temper embrittlement susceptibility of a 2.25 Cr-1.0 Mo welded joint by sustaining it through step cooling treatment. The welded joint was prepared by regulated metal deposition and GMAW process integrating with metal-cored wire. The study proposes in-depth research and serves as a base for the usage of metal-cored wires. Similarly, [PERSON] et al. [27] have performed a study on selected parameters for single bead metal deposition using the gas metal arc welding manufacturing technique. Near the welded region, ferrite with pearlite structures was observed. The upper layers of the weldment showed cracks and signs of porosity because of the increase in deposition height. Different hardness values were obtained on different wall structures, and surface defects by dye penetration tests and weight loss methods for corrosion behavior were also conducted. Due to rapid solidification, the topmost layers of both the square and circular walls were observed to be harder and brittle. To minimize post-processing and void, layer thickness, overlapping parameters and bead size of single-layer deposition were taken into consideration at the same time. As per the previous studies from researchers, WAAM for low alloy steel 1.25 Cr-0.5 Mo using metal-cored wires has not been researched properly. In the present study, bead-on-plate trials were taken on the base plate of low alloy steel following an experimental matrix produced through the Box-Behnken design (BBD). Wire feed speed, travel speed, and voltage were chosen as the input parameters and bead width and bead height were chosen as the output parameters. Furthermore, the robustness and adequacy of the obtained regression equations were analyzed by using analysis of variance (ANOVA). The teaching-learning-based optimization (TLBO) technique was then employed for single-response and multi-response optimization of BW and BH. To tackle the contradicting nature of responses, Pareto fronts were also generated, which provides a unique non-dominated solution. Validation trials were also conducted to reveal the ability and suitability of the TLBO algorithm. The optimum feasible settings for multi-layer metal deposition were determined after further tuning. The authors strongly consider this study to be very useful for industrial applications.