Effect of solidification mode on the nitric acid corrosion resistance behavior for weld deposited metal of high SiN austenitic stainless steel

• A novel type of high SiN austenitic stainless steel welding consumables was developed. • Austenitic stainless steel is subject to preferential corrosion of δ-ferrite in high-temperature, concentrated nitric acid corrosive environments that contain oxidizing ions. • During TIG welding, the solidification mode undergoes a transition from AF to FA with a Cr/Ni equivalent ratio ≥ 1.51. • Solidification mode affects corrosion behavior by changing the elemental segregation of the weld metal. By adjusting the Cr, Ni equivalent to regulate the δ-ferrite content in the austenitic stainless steel weld deposited metal bearing high Si and N. The effect of solidification mode on the corrosion performance of the weld deposited metal in the high-temperature, concentrated nitric acid solution containing oxidizing ions was investigated by employing characterization means including metallographic microscopy, scanning electron microscopy, and electron probe microanalysis. The results demonstrate a "υ"-shaped trend between the corrosion rate of the weld and the increase in δ-ferrite content. The minimum corrosion rate of 0.05066 mm/a was achieved at a δ-ferrite content of 5.5%. Galvanic coupling corrosion formed between δ-ferrite and austenite owing to their electrochemical potential difference, leading to preferential corrosion of δ-ferrite. Furthermore, the Cr equivalent (eq) /Ni eq ≥ 1.51 results in a transition of the weld solidification mode from Austenitic-Ferritic (AF) to Ferritic-Austenitic (FA). Concurrently, the corrosion rate undergoes a decline of approximately 13%. The corrosion morphology of the molten metal in the AF mode is characterized by a corrosion groove, whereas the corrosion morphology in the FA mode is typified by a corrosion pit.