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Alloy 400 v Hastelloy C276

Alloy 400 v Hastelloy C276

3 July 2024

We’re going to take a deep dive into a detailed comparison of two heavyweights in the world of nickel-based alloys: Monel Alloy 400 and Hastelloy C276. Both are widely used in the chemical processing industry where they are prized for their mechanical performance and corrosion resistance. They are, however, quite different alloys and contain different alloying elements. What impact do these differences have on mechanical and corrosion performance and the ease of machining and fabrication? Let’s find out…

Standards and Releases

Monel Alloy 400 is certified under British Standard BS3076 (NA13) and American Standard ASTM B164 (N04400). Hastelloy C276 meets American Standard ASTM B574 (N10276). Both can also comply with NACE MR-0175 requirements, ensuring they meet rigorous standards for resisting corrosion in challenging environments.

Chemical Composition

Ni Cu Mo Cr W Fe Mn Co C Si Others
Alloy 400
63-70
28-34
2.5
2
2
0.3
0.5
0.024
Hastelloy C276
Balance
15-17
14.5-16.5
3-4.5
4-7
1
2.5
0.01
0.05
0.37

Monel Alloy 400 depends heavily on the addition of copper within its composition, while Hastelloy C276 incorporates molybdenum, chromium, and tungsten, which provide stronger solution strengthening, resulting in higher tensile strength. The tighter control over impurities like silicon and carbon in Hastelloy C276 enhances its weldability, but, as always, there is no such thing as a free lunch and this also raises production costs.

Mechanical Properties

  Alloy 400 Hastelloy C276
UTS (MPa)
600
690
0.2% Proof Strength (MPa)
415
310
Elongation (%)
20
40
Hardness (HRC max %)
35
45
Condition
Cold worked and stress relieved
Cold worked and solution annealed

The alloying elements in Hastelloy C276 deliver greater tensile strength and hardness, making it suitable for high temperature applications where structural stability is crucial. At elevated temperatures the microstructure of any alloy becomes more unstable, which can lead to the possibility of phases precipitating that are harmful to the material. The careful use of additions in Hastelloy C276 mitigates this risk.

Corrosion Resistance

Both alloys are well regarded for corrosion resistance but their protection varies in different circumstances. Monel 400’s copper content excels in corrosion resistance in oxidising environments at normal temperatures but diminishes at higher temperatures. In contrast, the chromium and molybdenum in Hastelloy C276 provide robust oxidisation resistance even at higher temperatures, along with added protection in reducing atmospheres.

Physical Properties

  Alloy 400 Hastelloy C276
Density (g/cm3)
8.80
8.89
Thermal Conductivity (W/moC)
22.0
9.8
Young’s Modulus (GPa)
179
205

Applications

Both alloys are extensively used in the chemical processing industry. However, their applications vary:

  • Alloy 400: Ideal for valves, pumps, gasoline and freshwater tanks, process vessels, marine fixtures, and heat exchangers.
  • Hastelloy C276: Suited for heat exchangers, reaction vessels, evaporators, and even in the recovery of “sour” natural gas.

Conclusion

Monel Alloy 400 and Hastelloy C276 each offer excellent mechanical performance and corrosion resistance, with specific strengths tailored to different environments. Hastelloy C276 stands out in high-temperature and corrosive settings due to its sophisticated chemical composition, though this comes at a higher cost. The choice between these alloys depends on the specific application needs and budget.

Datasheets

Click here to download a Monel 400 / Alloy 400 datasheet

Click here to download a Hastelloy C276 datasheet

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