321 vs 347 Stainless Steel: Titanium vs Niobium Stabilization

 

How do their stabilizing elements differ?​

321 uses titanium (5×C min) for stabilization, while 347 uses niobium (8-10×C min). This difference affects their performance in high-temperature and corrosive environments.​

 

Which performs better at extreme temperatures?​

347 retains strength slightly better at temperatures above 800°C, making it suitable for long-term high-heat service. 321 is more stable in cyclic heat conditions, ideal for exhaust systems.​

 

How do they compare in corrosion resistance?​

Both resist intergranular corrosion after welding, with 321 offering slightly better resistance in mild chemicals. 347 has better resistance to high-temperature carburization, suitable for reducing atmospheres.​

 

What about their fabrication properties?​

321 is more ductile and easier to form than 347, making it better for complex shapes. 347 welds well with controlled heat input, maintaining its strength in welded joints.​

 

Where are 321 and 347 commonly used?​

321 is in aircraft exhaust systems and heat exchangers. 347 finds applications in nuclear reactor parts, furnace components, and high-temperature fasteners.