Joining of stainless steel with novel filler material and its weldability studies

Welding of Austenitic Stainless steels results in the emission of hexavalent chromium [Cr⁺⁶] fumes due to the presence of 18-22% chromium contents in the stainless steel base and filler materials. These hexavalent fumes are carcinogenic and can cause respiratory problems to the welders and personnel in the vicinity of welding. In the present research work novel Chromium free Nickel based filler material of %wt composition 41Ni, 8Co, 16Fe, 14Mo, 7Mn, 8Cu, 3Nb, 1Ti, 1Si, 1Al is developed and its weldablilty with stainless steel are studied. The micro-structure and chemical composition of different phases in the filler material and weld joints are studied using different microscopy and X-Ray Diffraction tools respectively. The ultimate tensile strength, hardness and impact strength of the filler material are 536 MPa, 190 VHN and 110 J respectively. The strength, average hardness and impact strength of weld joint welded are 483 MPa, 209 VHN and 89 J respectively. Results of Potentio-dynamic polarization and Inter Granular corrosion cracking (IGCC) of the weld joint have shown the corrosion rate of 1.575e-004 mills/year and 354.56 mills/year respectively. Mechanical properties and corrosion rate of weldments welded by novel filler material is compared with that of conventional filler material too. Design of experiments(DOE) using Taguchi L9 array is formulated to understand the influence of Welding current, weld plates root gap and gas flow rate on output parameters such as Tensile Strength, Impact strength and corrosion resistance of weldment. The analysis has also shown that welding current is the most influencing parameter out of remaining three input parameters. DOE using Response surface methodology has shown maximum Tensile strength of 487 MPa, maximum Hardness of 209 VHN and minimum corrosion rate of 1.575e-004 mills/years obtained with optimum current value of 130 A, 11.79 Liters/min gas flow rate and 2.33 mm root gap.