High Temperature Corrosion Studies X-ray Detraction Analysis on GTA Welded Dissimilar Metals of Inconel 718 and ASS 316

Oxidation and hot corrosion are major problems in marine, aircraft industries, petrochemical, thermal power plants, boiler part pressure vessel and land-based gas turbines etc. The surfaces of metals and alloys in oxidizing environments at high temperatures sometimes experience accelerated oxidation when they are covered with a thin fused salt layer. Due to the use of a wide range of tubes, increased operating temperatures can cause deterioration of the turbines. Inconel 718 and ASS 316 super-alloys (medium grade) are used as important materials for high-temperature conditions to avoid the problems of superalloys. In the current research, the Inconel 718 and Austenitic Stainless Steel (ASS) 316 (3 mm thick) are welded by using the GTAW process has conducted oxidation and hot corrosion studies are conducted on weldments. The Weldments and parenting were studied in the presence of air and molten salt climate (Na2SO4+V2O5). Air and molten salt studies were conducted in the laboratory furnace for 50 iterations, with 1-hour heating at 9500c, 10500c and 11500c in each cycle, then 20 minutes of cooling. The samples are critically examined and the change in weight is recorded at the end of each cycle.In the case of studies in molten salt environments, after heating the sample at 2000C, a uniform layer (3-5mg/cm2) of Na2SO4+V2O5 mixture is coated on the samples with the help of a camel hair brush. The chemical composition and morphologies of the oxide scales were confirmed using X-ray diffraction analysis. The oxidation resistance is not only related to the nature of the passivation film and also depends on the salt environment and the structure of the alloy. This hardness difference is caused by the formation of carbides during the welding thermal cycle. In environmental studies, TIG welding of molten salt (Na2SO4+50%V2O5) showed the lowest weight loss compared to the base metal. Corrosion rate is less as compared to base metals due to low weight loss of weldment. Major Findings: Overall the Weldment should be the weight gain as compared to un-welded base material in case of molten (Na2SO4+V2O5) environment study. The high temperature oxidation resistance is not only related to the nature of the passive film, but it is also strongly dependent on the salt environment and the structure of the alloy.