Hot Corrosion Demeanour of Key-Hole Plasma Arc Welded Aerospace Grade Hastelloy X in Molten Salts Environment

Abstract

<div class="section abstract"><div class="htmlview paragraph">The current work investigates the hot corrosion demeanour of Hastelloy X weldment produced with autogenous mode through key-hole plasma arc welding (K-PAW). The hot corrosion test has been performed for weldment in molten salt-1 (MS-1) (75 % Na<sub>2</sub>SO<sub>4</sub> + 25 % V<sub>2</sub>O<sub>5</sub>) and molten salt-2 (MS-2) (75 % Na<sub>2</sub>SO<sub>4</sub> + 20 % V<sub>2</sub>O<sub>5</sub> + 5 % NaCl) circumstance for 25 hrs (25 cycles) at 900 °C. The MS-1 substrate of both base metal and weldment provided the lowest weight gain than the MS-2 substrate. The NaCl in the MS-2 causes severe hot corrosion on the substrate, whereas the absence of NaCl in MS-1 reduces the hot corrosion effects. The highest parabolic constant is observed for K-PAW weldment in MS-2 condition. The tendency of hot corrosion rate follows the order of, Base Metal MS-1 < K-PAW MS-1 < Base Metal MS-2 < K-PAW MS-2. The occurrence of protective phases like chromium oxides (Cr<sub>2</sub>O<sub>3</sub>), spinel oxides (NiCr<sub>2</sub>O<sub>4</sub> and NiFe<sub>2</sub>O<sub>4</sub>) Nickel oxide (NiO) on the substrate resist the further oxidation. But, the development of MoO<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub> phases are increased the cracking as well as spallation rate which promotes severe corrosion of the substrates. The plasma arc welded substrate and base metal in MS-1 condition are giving better resistance than in MS-2 at 900 °C.</div></div>