UNS N06600 and UNS N06601 are both nickel-chromium plate alloys used in high-temperature equipment. The key difference is that 601 adds aluminium and more chromium to improve oxidation resistance at the very top of the temperature range.
Composition Compared
UNS N06600 contains about 72 percent nickel, 14 to 17 percent chromium and 6 to 10 percent iron. UNS N06601 contains about 58 to 63 percent nickel, 21 to 25 percent chromium and about 1.0 to 1.7 percent aluminium, with the balance iron.
The higher chromium and the aluminium addition in 601 promote a more protective oxide scale, while the very high nickel in 600 favours alkaline and high-purity water service.
High-Temperature Oxidation and Carburisation
UNS N06601 is specifically designed for resistance to oxidation, carburisation and scaling at high temperature, and it performs better than 600 in strongly oxidising or carburising atmospheres at the upper end of the range.
UNS N06600 still offers good oxidation resistance and is often selected where the atmosphere is more mildly oxidising or where a caustic environment is also present.
Mechanical Properties
Both alloys are solid-solution strengthened austenitic materials with good ductility and toughness, and both can be formed and welded. UNS N06601 has somewhat higher strength in the annealed condition due to its aluminium and higher chromium content.
Neither grade is precipitation hardened, so selection depends on the service environment rather than on a heat treatment step to raise strength.
Corrosion Resistance
UNS N06600 excels in caustic alkalies, high-purity water and many chloride environments and resists dry chlorine and hydrogen chloride at moderate temperature. UNS N06601 performs well in many oxidising chemical environments and is particularly valued for scaling resistance.
Where caustic or high-purity water conditions control the design, 600 is generally preferred; where high-temperature oxidation or carburisation dominates, 601 is the better choice.
Plate Availability and Selection
Both alloys are supplied as plate and sheet to flat-rolled product standards, with separate provision for the two grades. Plate thickness, width and edge condition should be stated on the order together with the applicable standard and edition.
For furnace internals, radiant tubes, heat treating fixtures and combustion components, choose according to the atmosphere: 601 for strongly oxidising or carburising conditions, 600 for caustic or high-purity water duty. Request test certificates with chemistry, mechanical results and heat traceability.
Frequently Asked Questions
Q: What is the main difference between UNS N06600 and UNS N06601?
UNS N06601 contains more chromium plus about 1.0 to 1.7 percent aluminium, which improves high-temperature oxidation resistance.
Q: Which plate grade resists oxidation better?
UNS N06601, whose chromium and aluminium content forms a more protective oxide scale at high temperature.
Q: Which grade is better in caustic service?
UNS N06600, because its very high nickel content gives excellent resistance to caustic alkalies.
Q: Are either of the plate grades precipitation hardened?
No. Both are solid-solution strengthened austenitic alloys.
Q: How should plate grade be selected?
Select 601 for strongly oxidising or carburising atmospheres and 600 for caustic or high-purity water duty, then confirm the product standard and thickness.
