Dilution Control in SMAW & GTAW Welds Involving Low Alloy Steel, Ferritic Stainless Steels & Nickel Based Alloys

Fusion welds of overlay were prepared between ferritic stainless steel of 410s with base metal of low alloy steel of SA 387 Gr. 11 Class 2 using Ni based consumables (Inconel 182 & 82) with GTAW & SMAW processes for clad restoration. For clad restoration, most of the process licensors indicate requirement of 3 mm undiluted clean chemistry throughout thickness as per ASME Sec. II, Part C to ensure sufficient corrosion resistant during operation of a coke drum. Experiments were carried out by varying different parameters that directly affect the dilution like chemical composition of filler wire, effect of bead height, overlap and layer by layer grinding for Inconel 182 electrode. For Inconel 82 filler wire, effect of wire feed rate and melting power on dilution control were studied. The dilution level of each weld fusion was determined through geometric measurements as well as through measuring chemical composition using optical emission spectrometer of the weld cross-sectional areas. Result states that reduction in electrode diameter plays a major role in reduction of dilution. Also, with increase in overlap, the weld metal chemistry tends to move towards filler metal chemistry. For GTAW process, filler metal feed rate & melting power individually do not contribute in reducing the effect of dilution however optimizing their combination yield required results. Also, effect of variation % Fe in weld overlay on corrosion resistance was examined using ASTM G 28 method A & for cyclic polarization with NaCl environment where rate of corrosion reduces drastically with reduction in dilution.