Understanding material equivalents is crucial for global sourcing, design substitution, and ensuring component performance. The material 2.4858 refers to a specific nickel-based alloy defined within the European Werkstoffnummer (Material Number) system (DIN/EN standard). This article clarifies the exact chemical composition of 2.4858 and lists its internationally recognized equivalent grades across major industrial standards like UNS, EN, ASTM/ASME, and common trade names.

What is 2.4858 Material?

The number 2.4858 identifies a nickel-chromium-molybdenum alloy strengthened with the addition of niobium (also known as columbium). Its primary characteristic is exceptional resistance to a wide range of severely corrosive environments, including oxidizing and reducing acids, saltwater, and high-temperature atmospheres. Key properties include:

• Excellent Corrosion Resistance: Performs well in pitting, crevice corrosion, and stress-corrosion cracking scenarios common in chemical processing and marine settings.
• High Strength at Elevated Temperatures: Maintains mechanical integrity and resists oxidation well above 1000°C (1832°F).
• Good Fabricability: Can be welded, machined, and formed using standard techniques, though it work-hardens rapidly.

This alloy achieves its properties through a precise balance of elements: Nickel (Ni) forms the base, Chromium (Cr) provides oxidation resistance, Molybdenum (Mo) enhances resistance to reducing acids and pitting/crevice corrosion, and Niobium (Nb) stabilizes the alloy against sensitization (intergranular corrosion) during welding and forms strengthening precipitates.

Core Chemical Composition of 2.4858

Regardless of the naming standard, the alloy we are discussing has the same fundamental chemical recipe:

• Nickel (Ni): Approximately 58% (base element)
• Chromium (Cr): 20.0 – 23.0%
• Iron (Fe): ≤ 5.0%
• Molybdenum (Mo): 8.0 – 10.0%
• Niobium + Tantalum (Nb+Ta): 3.15 – 4.15% (Nb is the primary contributor)
• Carbon (C): ≤ 0.10%
• Manganese (Mn): ≤ 0.50%
• Silicon (Si): ≤ 0.50%
• Phosphorus (P): ≤ 0.015%
• Sulfur (S): ≤ 0.015%
• Aluminum (Al): ≤ 0.40%
• Titanium (Ti): ≤ 0.40%
• Cobalt (Co): ≤ 1.00%
• Copper (Cu): ≤ 0.50%

Equivalent Grades to 2.4858

Finding the right equivalent depends on the standard used by your supplier, design specifications, or regional requirements:

1. UNS Number: N06625 (Most Common Identifier) The Unified Numbering System (UNS) is widely used in North America and internationally. The direct equivalent for Werkstoff 2.4858 is UNS N06625. This is the most critical equivalent for technical documentation and global procurement. When specifying material, providing UNS N06625 ensures clarity regardless of regional naming conventions.

2. European Standards: EN 2.4858 and NiCr22Mo9Nb Within the European EN (European Norm) system, the alloy retains the EN 2.4858 designation. It is also commonly referred to by its approximate chemical composition abbreviation: NiCr22Mo9Nb (indicating roughly 22% Cr and 9% Mo with Niobium). This name clearly reflects the key alloying elements.

3. ASTM/ASME Specifications The ASTM International (American Society for Testing and Materials) and ASME (American Society of Mechanical Engineers) standards define this alloy within various product forms. The most common designations under these standards are Alloy 625 (the generic name) or specifying the relevant material specification directly:

   • ASTM B564 / ASME SB-564: This specification covers nickel alloy forgings (forged fittings, flanges, valves), explicitly listing UNS N06625 (Alloy 625).
   • ASTM B443 / ASME SB-443: Covers nickel alloy plate, sheet, and strip for UNS N06625.
   • ASTM B444 / ASME SB-444: Covers nickel alloy seamless pipe and tube for UNS N06625.
   • ASTM B446 / ASME SB-446: Covers nickel alloy wire, rod, and bar for UNS N06625.
   • ASTM B704/B705 / ASME SB-704/SB-705: Covers welded pipe and tube made from UNS N06625.

4. Common Trade Names The most famous and widely used trade name for UNS N06625 / EN 2.4858 is Inconel 625. Originally developed by Special Metals Corporation (now part of Precision Castparts Corp., a Berkshire Hathaway company), "Inconel" is a trademark, and Inconel 625 has become synonymous with this specific alloy across many industries. Other manufacturers produce the same alloy composition under their brand names or generic "Alloy 625".

5. Other National Standards:

   • JIS (Japan): NCF 625 (This designation is less commonly encountered than equivalents like NCF 825 for other alloys).
   • GB (China): NS3306 (This is the Chinese national standard equivalent for UNS N06625 / NiCr22Mo9Nb).
   • PN (Poland): H625PW (This Polish designation specifically refers to the sheet/plate form).

Key Properties and Typical Applications

Thanks to its outstanding corrosion resistance and high-temperature strength, 2.4858 (N06625 / Alloy 625) is widely utilized in demanding sectors. Key mechanical properties include high tensile and yield strength, good ductility (elongation), and excellent fatigue strength. Its creep and rupture strength are particularly notable at elevated temperatures. Common applications span aerospace (engine components, ducting), chemical and petrochemical processing (reactors, heat exchangers, valves, pumps), marine engineering (propeller blades, seawater equipment), power generation (gas turbines, SCR systems), oil and gas (downhole components), and pollution control (flue gas desulfurization systems).

Why Rely on Equivalents?

Knowing that 2.4858 = UNS N06625 = EN NiCr22Mo9Nb = Alloy 625 = Inconel 625 is essential to avoid sourcing confusion or specifying incorrect materials. It allows engineers, designers, and procurement specialists to source materials globally based on readily available standards and certifications. Manufacturers provide material test reports (MTRs/Certificates of Conformity) listing the relevant specification (e.g., ASTM B564, EN 10204 3.1/3.2) and confirming the certified grade meets the required chemical composition and mechanical properties for the specific product form. Always refer to certified material documentation based on an established standard like ASTM, EN, ASME, or DIN to ensure you receive the correct 2.4858 equivalent grade material meeting your application requirements.