Dinesh Wasudeo Rathod

In recent years, cold metal transfer (CMT)-based wire arc additive manufacturing (WAAM) has gained significant attention in the manufacturing sector, particularly for its ability to produce components with low thermal input and high deposition rates. This study investigated the tribological behaviour of SS316L walls fabricated using CMT-based WAAM, employing a ball-on-plate linear reciprocating test with tungsten carbide (WC) counter body under varying thermal inputs and applied loads (15 N, 20 N, and 25 N). The tests were conducted for 10 minutes at a frequency of 15 Hz and a stroke length of 2 mm. Results indicate that the coefficient of friction (COF) increased slightly with applied loads, yielding an average COF of 0.22 across all loads. Wear rate analysis revealed that both increased applied load and heat input led to a higher wear rate, with the maximum wear rate (3.39 × 10⁻³ mm³/m) occurring at high heat input and 25 N, while the minimum wear rate (1.2 × 10⁻³ mm³/m) was observed at low heat input and 15 N. Vickers microhardness results demonstrated an inverse relationship between hardness and heat input, with hardness increasing by 11% as heat input decreased from high to low. FESEM analysis of wear tracks showed significant craters, abrasive grooves, delamination, surface cracks, and particle adhesion, identifying an abrasive-dominant wear mechanism with surface fatigue, partial adhesion, and oxidative wear. Wear debris analysis showed sharper angular particles and larger irregularly shaped flakes. X-ray diffraction (XRD) spectra confirmed δ-ferrite and γ-austenite phases pre- and post-wear, with post-wear analysis showing an α′-martensite peak, indicating phase transformation during wear.

Wire arc additive manufacturing (WAAM) has emerged as a promising and cost-effective method for producing components made from aluminum alloys, particularly in industries like aviation and aerospace. This process enables the fabrication of high-performance parts while minimizing manufacturing complexities. The demand for aluminum 7xxx series alloys is significant in these sectors due to their outstanding material properties. Efficient production methods, such as WAAM, are essential for utilizing these high-demand materials effectively. Despite the advantages of the WAAM process, challenges remain, particularly when layer-by-layer deposition of Al 7xxx (Al-Zn-Mg) alloys is considered. The high heat density generated during the arcing process can lead to issues such as zinc evaporation, hydrogen formation, and oxidation of the alloys. Additionally, the WAAM technique faces hurdles like delamination, porosity, hot cracking, and complex thermal cycles, all of which can adversely affect the performance of the components produced. This study aims to tackle the challenges associated with the WAAM process by employing Gas Metal Arc Welding techniques, while also exploring opportunities for further research in this area.

Additive manufacturing (AM) is revolutionizing production, enabling the customization of components for specific applications while promoting sustainable and on-demand manufacturing. This innovative method is especially valuable for producing intricate and custom parts from metallic materials like SS316L. Known for its excellent corrosion resistance and high strength, AISI 316L austenitic steel is widely utilized in aerospace, medical, automotive, and marine industries. This study explores the deposition of multi layered SS316L wall using the Cold Metal Transfer (CMT)-based Wire Arc Additive Manufacturing (WAAM) technique. The resultant multilayered wall exhibited seamless fusion devoid of macroscopic defects. A comprehensive analysis of its morphology, microstructure, mechanical properties, and tribological performance was conducted. Microstructural examination revealed a progression from fine equiaxed grains with ferrites in the lower sections to coarser columnar grains with acicular ferrites in the upper sections. Vickers microhardness and Charpy impact tests indicated a decline in hardness and impact energy from lower to upper sections. Uniaxial tensile tests demonstrated decreasing yield and ultimate tensile strengths, alongside significant ductility and toughness. The coefficient of friction and wear rate escalated with higher loads and from lower to upper sections, predominantly displaying abrasive wear mechanisms. These results validate the efficacy and durability of the SS316L CMT-based WAAM process in fabricating high-quality structures with tailored mechanical and tribological properties.

Deeper penetration in a gas tungsten arc welding process is the essential requirement for the fabrication of duplex stainless steel pipes. Activated fluxes and associated activated tungsten inert gas’ (A-TIG) welding process has proved itself as the better option for improved dilution and the deeper penetration. Use of hydrogen in shielding environment of A-TIG process for different ranges of activated fluxes needs to assess for deeper penetration and associated weld properties. Present investigation addresses the issue of deeper penetration using different activated fluxes in A-TIG process along with mixing of 2.5% H₂ in the argon gas shielding. An effect of H₂-induced shielding during CrO₃, MoS₂, TiO₂, and SiO₂ fluxes in A-TIG process has been investigated with weld pool morphology, depth of penetration, weld chemistry, scanning electron microscopy, optical microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The extra heat produced due to activated fluxes in H₂-induced shielding have been quantify in the study. The decomposed oxygen in the weld pool reacts with hydrogen in shielding and enhances the arc density. The growths of ferrite and austenite grains as well as the dendrite arm spacing have been significantly affected due to the presence of H₂ in the shielding. Oxide-based fluxes with H₂-induced shielding could promote the arc constriction behavior and Peclet number with enhanced heat density.

Weldability of duplex stainless steel (DSS) is an important issue in fabrication of pipes at petrochemical industries. Well-established tungsten inert gas (TIG) welding process has the limitations of lesser penetration; however, process parameters (such as current and voltage) need to increase to attain deeper penetration, which, in turn, affects the material’s property owing to increased heat energy. Use of activated fluxes generate the extra heat energy with same process parameters and causes the deeper penetration and increased dilution. The aim of the present study is to investigate the effect of activated fluxes on penetration, dilution, weld chemistry, weld microstructure, gas and slag metal reactions which has resulted from extra heat energy produced. Different activated fluxes were investigated in context of heat energy, associated penetration, dilution and weld pool properties. The oxygen content in activated flux has played significant role in hot cracking and void formations in the weld. Similarly, it also changes the surface tension gradient of weld pool considerably. Dendrite growth is predominant in oxide-based fluxes and this growth in austenite and ferrite dendrite has been evidenced as a function of oxygen content. The process with relevant mechanisms is elaborated in the present study.