Abstract The present work is focused on the influence of zinc trivalent plating on laser shot peened AISI 304 stainless steel samples to improve the corrosion resistance of the steel surface. AISI 304 steel samples were heat treated by annealing and polished to perform Laser Shot Peening (LSP) process using Nd-YAG laser functioning at a pulse interval of 10ns with different energies of 200 mJ, 300 mJ and 400 mJ on each sample. The highest magnitude of compressive residual stresses is induced using the pulse density of 2500 pulses/cm2. The laser treated sample was characterized by surface hardness using Vickers micro hardness test and surface morphology using an optical microscope and SEM analysis. The surface hardness of the sample is increased by increasing laser energy. The prepared zinc trivalent is plated using electro deposition on the laser treated surface by maintaining current between 1.5 to 4 amps/Dm2, and temperature between 20 to 40 deg C. MAHR’s roughness tests were performed to find the surface roughness of the sample. The surface roughness has drastically increased on zinc- coated samples compared to samples without coating. The Vickers micro hardness test conducted on zinc trivalent plated sample revealed the increase in hardness value of 200 mJ by 24% compared with 200 mJ sample without coating. SEM and EDAX were carried out to know the changes occurred in the chemical composition of the samples before and after coating.

This research work investigates the use of pulsed current for joining two dissimilar metals Monel 400 and AISI 304 using Pulsed Current Gas Tungsten Arc welding using three different filler metals such as ER309L, ERNiCu-7 and ERNiCrFe-3. Microstructure observations showed the presence of Partially Melted Zone (PMZ) at the heat affected zone (HAZ) of all the weldments. The formation of secondary phases was witnessed at the HAZ of Monel 400 on using ERNiCu-7 filler. Tensile studies corroborated that the bimetallic combinations employing ERNiCu-7 offer better tensile properties as compared to ER309L and ERNiCrFe-3 weldments. Parent metal Monel 400 exhibited better corrosion resistance as compared to other zones of the weldments when exposed in the synthetic molten salt environment containing Na2SO4 - 60% V2O5 environment at 600 °C. A detailed structure - property relationship was made using the combined techniques of optical microscopy and SEM. Also the hot corrosion products were revealed using the thermogravimetric plots, XRD and SEM/EDAX analysis.