Hot Corrosion of Weldments

Hot corrosion of the weldment is the result of the reaction between oxidation and sulfidation, which affects welded joints exposed to combustion gases containing sulfate coal ash at high temperature. It is also demonstrated that welding processes, weld consumables, temperature of exposure, and mixture of salt environment are important factors in hot corrosion of the weldment

Hot corrosion behavior of monel 400 and AISI 304 dissimilar weldments exposed in the molten salt environment containing Na2SO4 + 60% V2O5 at 600 °C

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

Effect of grain boundary precipitation on the mechanical integrity of EBW joints of Inconel 625

The precipitation effects on the mechanical behavior of electron beam welded joints of Inconel 625 in the as-welded [AW] and post-weld heat treatment [PWHT] conditions have been investigated in this research study. A PWHT comprising of direct aging [DA] treatment at 700 °C for 100 h in vacuum at a pressure of 10−5 mbar was performed on the weld joints. The microstructure of the base alloy opined the precipitation of MC system carbides and γ′′ strengthening phase after subjecting to DA. Also, Nb–Mo rich precipitates and the Laves phase was noticed in the inter-dendritic arms of the fusion zone (FZ) of welded joints in the AW conditions. DA treatment has a notable effect on the weld mechanical characteristics of Inconel 625 joints. The precipitation of γ′′ strengthening phase is reasoned for the significant rise in the yield strength [YS] and tensile strength [TS] of the base alloy and EBW joints

Comparative Studies of High and Low Frequency Pulsing on the Aspect Ratio of Weld Bead in Gas Tungsten Arc Welded AISI 304L Plates

AbstractThis research article presents the optimization of process parameters for pulsed current gas tungsten arc welded austenitic stainless steel AISI 304L of 4mm thickness. Investigations were carried out to study the effect of frequency with respect to penetration and bead width to penetration ratio (Aspect Ratio).Three level 4 factor Taguchi L9 orthogonal array was used to carry out the bead on plate welds. Taguchi analysis was done for main effects plot to optimize the process parameters and ANOVA was used to find the percentage contribution of each factor and their responses. The key findings of the article elucidated that full penetration with optimized aspect ratio could be achieved on employing high frequency pulsing