The escalating necessity for more efficient and defect-free joining of ‘ultra-thin foil collectors-to-tabs’ in electric vehicle (EV) Li-ion pouch cells motivates this study. The prevalent ultrasonic welding (USW) method for these joint types, faces limitations such as design constraints and access requirements, laser welding (LW) emerges as a promising alternative offering flexibility, one-side access and faster speeds with efficient heat input. This study aims to investigate the feasibility of LW as a viable alternative to USW for joining current collectors-to-tab joints. It compares the mechanical, metallurgical, electrical and thermal analysis of the joints to evaluate both welding techniques for joint defects. The comparison of solid-state material mixing during USW and the intermixing of aluminium (Al) and copper (Cu) during fusion LW using EDX analysis presents interesting observations in the study. The USW generates a thin transition layer with intermetallic compounds (IMCs) attributed to the diffusion of Cu into the Al matrix during joining, which is comparatively lower as in the case of LW with higher material mixing with brittle IMCs like Al₂Cu and Al₄Cu₉. However, the joint strength of LW is comparatively lower than the USW joint attributed to the reduced fusion zone area. Furthermore, from the electrical contact resistance and the joint temperature analysis, it was found that the resistance and temperature vary by as much as 13% and 6%, respectively, for the 50 A and 75 A passing currents when the USW is replaced with the LW process.

This paper investigated various aspects of replacing existing micro-resistance spot welding (micro-RSW) with micro-laser spot welding for joining Inconel 718 thin foils to thick 410 steel stack-up to allow faster, non-contact joining together with flexibility in spot positioning and removal of tip dressing required for RSW electrodes. The joint quality was evaluated based on the mechanical strength, microstructural characteristics and joint strength at elevated temperature as these joints are often used for high-temperature applications. Experimental investigations were performed using micro-RSW and micro-laser spot welding to obtain the 90° peel and lap shear specimens, each comprising four spots. The obtained strength from laser joints was significantly higher than that of micro-RSW joints due to larger weld nugget formation and interface width. The process map for obtaining good quality welds was also identified, and about a 17% reduction in joint strength was obtained when welded specimens were subjected to elevated temperature (i.e., 500 °C) in comparison with room temperature. This reduction was compensated for using the flexibility of laser welding to add two extra spots. The overall performance of the micro-laser spot welds was found to be better than the micro-RSW considering joint strength, flexibility in placing the spots and time to produce the welds.

The High Velocity Oxyfuel (HVOF) system has established itself as a leading process for depositing NiCoCrAlY and MCoCrAlX coatings, which serve as a crucial bond coat in the Thermal Barrier Coating system (TBC) for high temperature applications. By providing exceptional protection against hot corrosion, oxidation and wear, these coating have become ideally suited for aerospace components and gas turbine applications. Recent advancements have primarily focused on enhancing coating performance through strategies such as pre-oxidation, implementation of multilayers and graded structures, vacuum heat treatment, rare earth doping and oxide dispersion strengthening. These modifications ultimately result in improved grain refinement, adhesion, superior thermal stability and enhanced mechanical properties. This article will provide significant development in HVOF-sprayed MCrAlX/NiCoCrAlY coatings with particular focus on microstructural evolution, durability and process optimization under extreme environmental conditions.

In this paper, the influence of various laser wobbling patterns, such as circle, ellipse, figure eight, bowtie, Celtic, flower, atomic, hexagon, triangle and star, on grain refinement mechanisms during welding of Inconel 625 sheets is evaluated. An in-depth analysis of molten pool stirring mechanisim during welding was addressed to understand the effectiveness of wobble patterns in grain refinement and fusion zone (FZ) strengthening. The dynamic stirring effect of the laser beam’s wobble motion significantly influences the solidification process and resulting microstructure. Laser spot trajectories and temporal energy deposition were analyzed to elucidate their impact on the FZ. Electron backscatter diffraction (EBSD) micrographs showed significant grain refinement during the welding. However, the wobbling patterns with elliptical and flower-type paths resulted in coarse equiaxed grains with an average grain size of ~ 52 µm. Furthermore, the optimal patterns for refining the grain structure of Inconel 625 superalloy during laser welding are circular and atomic-type wobble patterns with grain refinement of ~ 35%. These findings highlight the potential of tailored laser wobble patterns for optimizing weld quality through controlled grain nucleation and refinement.

The inspection of the quality of welds in battery packs plays an important role in ensuring safety during the manufacturing and operation of energy-storage devices in automotive vehicles during service. This research investigated the novel application of laser Doppler vibrometry, a widely used non-destructive optical technique for modal analysis, to the post-weld evaluation of micro-TIG-welded interconnections in lithium-ion supercells. The experimental modal analysis showed features in the modal models of the supercells that were unique to their welding conditions. The comparisons between the supercells showed an absence of linear correlations between the modal parameters and the welding current, as well as differences in the welding parameters obtained from the negative and positive terminals of the cylindrical cells. These findings suggested that the modal parameters of the supercells were more strongly influenced by the rigidity of the structural materials than by the localized compliance of the welded interconnections. While this investigation demonstrated a method for using laser Doppler vibrometry to distinguish between different welding conditions in lithium-ion supercells at a structural level, further development is needed to identify the weld quality of individual interconnections.