𝙎𝙚𝙣𝙨𝙞𝙩𝙞𝙯𝙖𝙩𝙞𝙤𝙣 𝙋𝙝𝙚𝙣𝙤𝙢𝙚𝙣𝙤𝙣 𝙞𝙣 𝙎𝙩𝙖𝙞𝙣𝙡𝙚𝙨𝙨 𝙎𝙩𝙚𝙚𝙡 𝙒𝙚𝙡𝙙𝙞𝙣𝙜

𝙎𝙚𝙣𝙨𝙞𝙩𝙞𝙯𝙖𝙩𝙞𝙤𝙣 𝙋𝙝𝙚𝙣𝙤𝙢𝙚𝙣𝙤𝙣 𝙞𝙣 𝙎𝙩𝙖𝙞𝙣𝙡𝙚𝙨𝙨 𝙎𝙩𝙚𝙚𝙡 𝙒𝙚𝙡𝙙𝙞𝙣𝙜

During welding of austenitic stainless steels, exposure in the temperature range of 450–850 °C can lead to sensitization (also known as intergranular corrosion and weld decay).

 𝗠𝗲𝗰𝗵𝗮𝗻𝗶𝘀𝗺:

🔸At these temperatures, chromium carbide (Cr23C6) precipitates preferentially at the grain boundaries.

🔸This precipitation causes chromium depletionin adjacent regions (<12 wt% Cr).

🔸Since a minimum of ~ 12% chromium is required to maintain the passive oxide film, these zones become highly susceptible to intergranular corrosion (IGC).

 𝗜𝗻𝗳𝗹𝘂𝗲𝗻𝗰𝗶𝗻𝗴 𝗙𝗮𝗰𝘁𝗼𝗿𝘀:

🔸Carbon content: Higher C increases susceptibility due to more carbide formation.

🔸Thermal cycle: Slow cooling or multiple passes increase time in the sensitization range.

🔸Grain size: Coarser grains reduce boundaries areas for carbides.

🔸Welding process & heat input: GTAW/SMAW with high heat input can promote sensitization if not controlled.

𝗠𝗶𝘁𝗶𝗴𝗮𝘁𝗶𝗼𝗻 𝗦𝘁𝗿𝗮𝘁𝗲𝗴𝗶𝗲𝘀:

🔸Use low-carbon grades (304L, 316L) or stabilized grades (321 with Ti, 347 with Nb) to tie up carbon.

🔸Apply controlled heat input & interpass temperatures to limit time in the sensitization range.

🔸In critical applications, conduct post-weld solution annealing followed by rapid quenching.

🔸Perform ASTM A262 Practice E (Strauss Test) to detect susceptibility to IGC.