Table of Contents
Inconel 625 and Incoloy 825 are both corrosion-resistant nickel-based alloys, but they differ in chemical composition, mechanical strength, temperature tolerance, and applications. While both alloys are used in harsh environments, each serves distinct industrial purposes due to their unique properties. This article explains the key differences between Inconel 625 and Incoloy 825, with detailed comparisons in tables to aid in material selection for engineering, manufacturing, and procurement professionals.
Chemical Composition
The primary difference lies in their alloying elements. Inconel 625 contains higher levels of molybdenum and niobium, which enhance its high-temperature and high-stress resistance. Incoloy 825, on the other hand, includes iron and copper, improving its resistance to sulfuric and phosphoric acid environments.
| Element | Inconel 625 (%) | Incoloy 825 (%) |
|---|---|---|
| Nickel (Ni) | 58.0 min | 38.0 – 46.0 |
| Chromium (Cr) | 20.0 – 23.0 | 19.5 – 23.5 |
| Molybdenum (Mo) | 8.0 – 10.0 | 2.5 – 3.5 |
| Iron (Fe) | 5.0 max | 22.0 min |
| Niobium + Tantalum (Nb+Ta) | 3.15 – 4.15 | — |
| Copper (Cu) | — | 1.5 – 3.0 |
| Titanium (Ti) | — | 0.6 – 1.2 |
Mechanical Properties
Inconel 625 is stronger at elevated temperatures and has a higher yield strength, making it ideal for aerospace and high-stress components. Incoloy 825, while less strong, offers stable performance in acidic conditions and moderate temperatures.
| Property | Inconel 625 | Incoloy 825 |
|---|---|---|
| Tensile Strength (MPa) | 827 – 1034 | 586 – 758 |
| Yield Strength (MPa) | 414 – 517 | 221 – 310 |
| Elongation (%) | 30 – 45 | 30 – 40 |
| Hardness (HB) | 200 – 250 | 140 – 180 |
Corrosion Resistance
Inconel 625 offers exceptional resistance to oxidation and high-temperature corrosion. Incoloy 825 is optimized for corrosion in acidic environments, such as sulfuric and phosphoric acids.
| Environment | Inconel 625 | Incoloy 825 |
|---|---|---|
| Seawater | Excellent | Excellent |
| Oxidizing Acids | Excellent | Good |
| Reducing Acids | Good | Excellent |
| High-Temperature Oxidation | Excellent | Moderate |
Applications
The applications for each alloy vary based on their unique strengths. Inconel 625 is widely used in aerospace, marine, and nuclear industries, while Incoloy 825 is common in chemical processing and pollution control systems.
| Industry | Inconel 625 Applications | Incoloy 825 Applications |
|---|---|---|
| Aerospace | Jet engine components, turbine seals | — |
| Oil & Gas | Risers, manifolds | Piping systems, storage tanks |
| Chemical Processing | Reactor vessels, heat exchangers | Acid production, pollution control |
| Marine | Seawater piping, offshore equipment | Condensers, seawater systems |
Price Difference
Inconel 625 is more expensive due to its higher alloy content and better mechanical performance. Incoloy 825 is more cost-effective for applications that don't require extreme high-temperature strength.
| Product Form | Inconel 625 Price (USD/kg) | Incoloy 825 Price (USD/kg) |
|---|---|---|
| Rod | 95 – 125 | 65 – 85 |
| Sheet | 90 – 120 | 60 – 80 |
| Pipe | 100 – 130 | 70 – 90 |
Frequently Asked Questions
1. Which alloy is better for high-temperature applications?
Inconel 625 performs better in high-temperature environments due to its higher strength and oxidation resistance.
2. Is Incoloy 825 more cost-effective than Inconel 625?
Yes, Incoloy 825 is typically less expensive and ideal for environments where extreme mechanical strength is not required.
3. Can Incoloy 825 replace Inconel 625 in all applications?
No, Incoloy 825 lacks the high-temperature strength of Inconel 625 and is best used in moderately corrosive, lower-temperature environments.