Fundamental Difference
The main difference between Inconel 600 and Hastelloy C276 lies in their design targets. Inconel 600 exhibits excellent high-temperature oxidation resistance and is commonly used in gas turbines, furnace hardware and nuclear service, while Hastelloy C276 performs better in highly corrosive environments, especially reducing acids, and is the standard choice for chemical, marine and pollution control applications. In brief, 600 is a high-temperature alloy and C276 is a corrosion alloy.
Chemical Composition
Inconel 600 contains nickel 72.0% minimum, chromium 14.0-17.0%, iron 6.0-10.0%, carbon maximum 0.15%, manganese maximum 1.0%, silicon maximum 0.50%, sulfur maximum 0.015% and copper maximum 0.50%. Hastelloy C276 contains nickel as balance at about 57% typical, chromium 14.5-16.5%, molybdenum 15.0-17.0%, tungsten 3.0-4.5%, iron 4.0-7.0%, cobalt maximum 2.5%, carbon maximum 0.01%, silicon maximum 0.08%, manganese maximum 1.0%, phosphorus maximum 0.04%, sulfur maximum 0.03% and vanadium maximum 0.35%. The critical differences are the high molybdenum and tungsten content of C276, which drive its resistance to pitting, crevice corrosion and reducing acids, and the ultra-low carbon content of C276, which prevents sensitization in welded structures.
Physical and Mechanical Properties
Density is 8.47 g/cm³ for Inconel 600 and 8.89 g/cm³ for C276. Inconel 600 has roughly twice the thermal conductivity of C276, about 21.4 W/m·K at 100°C versus 11.1 W/m·K, and a higher coefficient of thermal expansion. Modulus of elasticity is similar at room temperature, around 207 GPa for 600 and 205 GPa for C276. Both alloys are suitable for high-temperature service; C276 is essentially non-magnetic in the annealed condition, with a magnetic permeability of 1.001 or less, while Inconel 600 is slightly magnetic at 1.01-1.10, making C276 preferred where strict non-magnetic properties are required.
Corrosion Resistance Comparison
Inconel 600 offers excellent resistance to alkaline solutions, fresh water and atmospheric corrosion, and its chromium-rich passive film excels in strong oxidizers such as nitric and chromic acids; however, its resistance to reducing acids such as hydrochloric and sulfuric acid is limited. Hastelloy C276 offers outstanding resistance across a much wider pH range, with excellent performance in reducing acids, oxidizing media, seawater and chloride environments. Its pitting resistance equivalent number is far higher than that of Inconel 600, giving exceptional resistance to pitting, crevice corrosion and chloride stress corrosion cracking. In high-temperature corrosion, both alloys provide good oxidation resistance, with Inconel 600 excellent to about 1095°C; C276 also resists carburization well due to its silicon content.
Fabrication and Selection Guidance
Both alloys are weldable. Inconel 600 welds easily and is widely used in the annealed condition, while C276 requires clean fabrication practice, and its ultra-low carbon content virtually eliminates intergranular attack in welded condition. Select Inconel 600 for high-temperature oxidizing service, caustic processing, furnace components and nuclear steam generator tubing where the environment is not severely acidic. Select Hastelloy C276 for chemical processing reactors, heat exchangers, flue gas desulfurization and marine equipment facing mixed acids, wet chlorine, chlorides and other aggressive media, and where non-magnetic properties or maximum localized corrosion resistance are required.
FAQ
Q: What is the main difference between Inconel 600 and Hastelloy C276?
A: Inconel 600 is a nickel-chromium alloy optimized for high-temperature oxidation resistance, while Hastelloy C276 is a nickel-molybdenum-chromium alloy optimized for corrosion resistance in reducing acids and aggressive chloride environments.
Q: Which alloy has better pitting resistance?
A: Hastelloy C276, whose high molybdenum and tungsten content gives exceptional pitting and crevice corrosion resistance, far exceeding that of Inconel 600.
Q: Is Inconel 600 resistant to hydrochloric acid?
A: No, Inconel 600 has poor to limited resistance to reducing acids such as hydrochloric acid; Hastelloy C276 is the industry benchmark for such service.
Q: Which alloy should be used for caustic soda service?
A: Inconel 600 is often preferred for pure caustic service because of its excellent resistance to hot alkalis.
Q: Are these alloys magnetic?
A: Inconel 600 is slightly magnetic in the annealed condition (permeability about 1.01-1.10), while Hastelloy C276 is essentially non-magnetic with permeability of 1.001 or less.
Q: What are the UNS numbers for these alloys?
A: Inconel 600 is UNS N06600 and Hastelloy C276 is UNS N10276.
