An in-house developed continuous wave CO 2 laser-based rapid manufacturing was deployed to fabricate porous structures of Inconel-625 using a new cross-thinwall fabrication strategy. Studies on the mechanical and metallurgical properties of these porous structures were carried out with laser energy per unit traverse length in the range of 150-300 kJ/m, powder fed per unit traverse length in the range of 16.67-36.67 g/m and transverse traverse index in the range of 0.7-1.3. The processing parametric dependence showed that the powder fed per unit traverse length was a predominating parameter in determining the porosity of the structures, followed by transverse traverse index and laser energy per unit traverse length. The compression testing of fabricated porous structures showed that the material had anisotropy up to 20% for 0.2% yield strength. It was found that the yield strength of the fabricated structures followed the power law and decreased from 423±8 MPa for 2.63±0.14% porosity to 226± 6.8 MPa for 11.57±0.52% porosity. Scanning electron microscopy showed that shape of the pores was triangular due to the cross-thin-wall fabrication strategy and the observed values of microhardness were in the range 256-370 VHN 0.98N . These studies are expected to augment our knowledge on the fabrication of porous structures with independent control on porosity and yield strength, which are important prerequisites for some of the prosthetic and engineering components in niche areas of applications.

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Experiments are conducted to deposit SS304 L powders on SS316 plates by plasma transfer arc welding process with varying four input process parameters, namely scanning speed, powder feed rate, stand-off distance, and current. The effects of these four input process parameters on deposition geometry, dilution, and bead continuity are investigated in this study. Attempts have been made to explain the experimental results with only two compound parameters, ''energy deposition per length'' and ''powder deposition per length'' instead of four independent input process parameters. It is observed that the variation of dilution is very little when the scanning speed increases from 100 to 600 mm/min and other process parameters remain constant. When the powder feed rate increases and other parameters remain constant, initially the dilution decreases rapidly and attains a minimum value which do not change further with increase in powder feed rate. It is also observed that the dilution remains almost constant around 6-9% as the stand-off distance changes from 7 to 11 mm and other process parameters remain constant. The formation of nonuniform bead is found to be due to insufficient energy deposition per length per mass of supplied powder.

This study investigates the role of thermal energy in deposition of thick layer of powder material by PTAW process. For analysis, stainless steel material powder of grade SS304L are laid on the substrate of grade SS316. The energy required for melting the powder and available for the substrate are calculated considering losses during deposition. The effects of input process parameters i.e. energy, scanning speed, powder feed rate are investigated on bead characteristics and dilution.

Joining of dissimilar metals leading to better material utilization with improved functionality encouraged the research thrust on various dissimilar material joining processes including laser brazing. This papers reports the development of laser brazing joints and their characterization for 3 mm thick Cu sheet with 3 mm thick AISI 316L stainless steel (SS) sheet in butt joint configuration using 63Ag-35.25Cu-1.75Ti active brazing foil as filler metal. Comprehensive experiments were carried out to identify the optimum processing parameters for controlled simultaneous heating of the filler metal and sh-7eets by laser beam resulting in melting of the filler metal without melting Cu and SS sheets. Using this methodology, a number of brazed joints were successfully prepared at different set of processing parameters. The brazed joints were subjected to various non-destructive (visual and dye-penetrant test) and destructive (microscopic examination, energy dispersive spectroscopy, four point bend testing etc.) characterization techniques. The results demonstrated that laser energy per unit length of 100 J/m is threshold limit for feasibility of brazing process for selected metal and thickness combination. Microscopic studies of transverse section of laser brazed joint showed full penetration across the thickness without the melting of parent metals. EDS studies showed the diffusion of filler material (Ag) more towards the Cu sheet as compared to that of SS sheet. Four point bend test showed that the alignment of laser beam-metal joint was critical for the brazing joint strength and improved joint strength was achieved when the beam was at the centre of the brazing joint. A maximum joint strength of 343.7 MPa was achieved for laser power of 550 W at scan speed of 3 mm/min.