Which is better Alloy 400 or alloy C-276?
Alloy 400 vs. Hastelloy C276
We're going to take a closer look at the two heavyweights in the world of nickel alloys: Monel Alloy 400 and Hastelloy C276. Both alloys are widely used in the chemical processing industry and are highly regarded for their mechanical properties and corrosion resistance. However, they are completely different alloys, containing different alloying elements. How do these differences affect the mechanical and corrosion properties, as well as the ease of processing and fabrication? Let's find out…
Standards and Releases
Monel Alloy 400 is certified to British Standard BS3076 (NA13) and American Standard ASTM B164 (N04400). Hastelloy C276 complies with American Standard ASTM B574 (N10276). Both alloys also meet NACE MR-0175 requirements, ensuring they meet stringent standards for corrosion resistance 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 |
While Monel Alloy 400 depends heavily on the addition of copper to its composition, Hastelloy C276 contains molybdenum, chromium, and tungsten, which provide greater solid solution strengthening, resulting in higher tensile strength. Hastelloy C276's tight control of impurities such as silicon and carbon improves its weldability, but as nothing comes for free, it also increases 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 provide increased tensile strength and hardness, making it suitable for high temperature applications where structural stability is critical. At high temperatures, the microstructure of any alloy becomes more unstable, which can lead to phase precipitation that is detrimental to the material. Careful use of the additives in Hastelloy C276 can reduce this risk.
Corrosion Resistance
Both alloys are known for their corrosion resistance, but their protection differs in different situations. The copper content of Monel 400 provides excellent corrosion resistance in oxidizing environments at room temperature, but this decreases at higher temperatures. In contrast, the chromium and molybdenum in Hastelloy C276 provide strong oxidation resistance even at higher temperatures and provide additional protection in reducing atmospheres.
Applications
Both alloys are widely used in the chemical processing industry. However, their applications vary:
Alloy 400: Suitable for valves, pumps, gasoline and fresh water tanks, process vessels, marine equipment and heat exchangers.
Hastelloy C276: Suitable for heat exchangers, reaction vessels, evaporators and even for the recovery of "sour" natural gas.
