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Inconel 600 for pressure vessels

Alloy 600 provides good resistance to general corrosion and is used employed in the light water reactor power units such as in PWRs and boiling water reactors or BWRs. The alloy is used in steam producer tubes, nozzles, pressurized heater sleeves, instrument nozzles and other components in PWR units. The reasons for choosing Inconel 600 for the pressure vessels are:

  1. Good mechanical characteristics similar to austenitic stainless steels.
  2. The alloy can be produced into various forms such as sheets, tubes, forgings, bars and casting for use in the power production sector.
  3. It welds to itself and also with carbon, low alloy and austenitic steel types.
  4. Alloy 600 is a mono-phase material that doesn’t need post weld heat processing. When it is heat processed after welding for low alloy steel components ready for welding, the received sensitization doesn’t make it susceptible to chloride corrosion as occurs in austenitic stainless steels that are subjected to heat processing.
  5. Alloy has good resistance to general corrosion in the elevated temperature water media causing nominal corrosion of walls.
  6. Extreme resistance to chloride induced stress corrosion cracking and superior resistance to caustic SCC as compare to austenitic steel grades.
  7. The thermal expansion characteristics are intermediate of carbon steels and austenitic steel grades therefore it is a suitable transition metal between these steel types.

Due to outstanding resistance to Stress corrosion cracking in the chloride media, Inconel 600 has been being chosen for steam generator tubing for PWPs since 1950s.