Is Inconel 925 Magnetic?

When it comes to high-performance alloys used in demanding industrial applications, Inconel 925 is one of the most recognized materials in the nickel-based alloy family. Known for its outstanding strength, corrosion resistance, and durability in extreme environments, Inconel 925 is widely used in oil and gas extraction, marine systems, and chemical processing.

One common question engineers and buyers often ask is: “Is Inconel 925 magnetic?”

The short answer is that Inconel 925 is generally non-magnetic in its annealed condition, but its magnetic response can vary slightly depending on its processing and heat treatment.

In this detailed guide, SASAALLOY explains the magnetic behavior of Inconel 925, the science behind it, and how it compares to other nickel-based and stainless steel alloys.

1. Understanding Magnetism in Alloys

Before discussing Inconel 925 specifically, it’s important to understand how magnetism works in metals. Magnetism is determined by a metal’s crystal structure and electron configuration.

Ferromagnetic Materials

Metals like iron, nickel, and cobalt have unpaired electrons that align in magnetic fields, making them strongly magnetic.

Paramagnetic Materials

These materials are weakly magnetic when exposed to an external magnetic field, but they do not retain magnetism once the field is removed.

Non-Magnetic (Austenitic) Materials

Alloys with a face-centered cubic (FCC) crystal structure, such as most nickel-based superalloys, do not allow unpaired electron alignment. As a result, they are non-magnetic or very weakly magnetic.

2. What Is Inconel 925

Inconel 925 (UNS N09925) is a nickel-iron-chromium alloy designed to provide both high strength and excellent corrosion resistance in harsh environments. It is part of the Inconel family and is developed specifically for oilfield components and marine equipment that encounter hydrogen sulfide (H₂S), carbon dioxide (CO₂), and chlorides.

Chemical Composition (Typical, Weight Percent)

• Nickel (Ni): 42–46

• Iron (Fe): 22–30

• Chromium (Cr): 19.5–23.5

• Molybdenum (Mo): 2.5–3.5

• Copper (Cu): 1.5–3.0

• Titanium (Ti): 1.9–2.4

• Aluminum (Al): 0.1–0.5

• Carbon (C): ≤ 0.03

• Manganese (Mn): ≤ 1.0

• Silicon (Si): ≤ 0.5

This carefully balanced chemistry ensures a precipitation-hardenable alloy that combines corrosion resistance with mechanical strength — a feature rare among standard stainless steels.

3. Is Inconel 925 Magnetic

In its annealed and aged conditions, Inconel 925 is essentially non-magnetic.

This non-magnetic nature is due to its austenitic (face-centered cubic) crystal structure, which remains stable even after heat treatment. The high nickel content (about 45 percent) dominates the alloy’s magnetic behavior, neutralizing the magnetic effects of iron.

However, the alloy may show a very weak magnetic response if:

• It is heavily cold-worked or deformed.

• Minor ferrite or martensite phases form during improper heat treatment.

In normal industrial applications, Inconel 925 is classified as non-magnetic, making it suitable for equipment and instruments that require low magnetic permeability.

4. Why Inconel 925 Is Non-Magnetic

The magnetic behavior of any metal depends largely on its microstructure.

• Inconel 925 has an FCC (face-centered cubic) crystal structure, which does not support magnetic domain alignment.

• Its high nickel content stabilizes the austenitic structure, ensuring it remains non-magnetic even after heat treatment.

• During age-hardening, precipitates of Ni₃(Ti,Al) form within the alloy. These strengthening phases also do not contribute to magnetism.

Thus, Inconel 925 maintains low magnetic permeability across a wide temperature range, even when exposed to mechanical stress or heat.

5. Comparison with Other Inconel and Stainless Steel Alloys

Inconel 625 and 718

• Both are nickel-based alloys like Inconel 925 and are also non-magnetic.

• Inconel 718 may develop slight magnetic properties after precipitation hardening, but the effect is minimal.

Inconel 825

• Chemically similar to Inconel 925 but not age-hardenable.

• Also non-magnetic, making it suitable for chemical and marine equipment.

Stainless Steel 316

• Austenitic stainless steels such as SS316 are mostly non-magnetic.

• However, cold-working can introduce a small amount of magnetism due to strain-induced martensite.

Ferritic or Martensitic Stainless Steels

• Alloys such as 410, 420, and 430 are strongly magnetic because of their body-centered cubic (BCC) or body-centered tetragonal (BCT) structure.

Summary: Compared to most stainless steels, Inconel 925 offers higher strength, better corrosion resistance, and more stable non-magnetic properties.

6. Heat Treatment and Magnetism

Inconel 925 undergoes two main heat treatment steps:

1. Solution Annealing (at 980–1020°C): Dissolves alloying elements into a solid solution and eliminates residual stresses. The structure after annealing is fully austenitic and non-magnetic.

2. Age-Hardening (Precipitation Hardening) (at 720–760°C): Forms strengthening precipitates of Ni₃(Ti,Al). This process does not significantly affect magnetism since these precipitates are non-ferromagnetic.

Improper heat treatment or exposure to very high temperatures may create minute quantities of secondary phases, but even then, the overall magnetic permeability remains extremely low — typically less than 1.02 μr (relative magnetic permeability).

7. Industrial Importance of Non-Magnetic Properties

The non-magnetic nature of Inconel 925 makes it ideal for use in applications where magnetic interference must be avoided or minimized.

Key Advantages

• Ensures reliable operation of electronic sensors and instruments.

• Suitable for downhole equipment where magnetic fields could interfere with measurement devices.

• Prevents distortion of magnetic readings in surveying and navigation equipment.

• Compatible with non-destructive testing methods such as eddy current inspection.

In fields like oil exploration and subsea engineering, low-magnetic materials are essential for precise measurements and safe operations.

8. Physical and Magnetic Properties Summary

Here are typical physical characteristics of Inconel 925:

• Density: 8.14 g/cm³

• Melting Range: 1340–1380°C

• Elastic Modulus: 200 GPa

• Thermal Conductivity: 11 W/m·K

• Relative Magnetic Permeability: 1.00–1.02

These values confirm that Inconel 925 behaves as a non-magnetic alloy, maintaining stable performance even under variable magnetic or thermal conditions.

9. Corrosion and Mechanical Performance

Although the main focus here is magnetism, it’s worth noting that Inconel 925’s corrosion and mechanical behavior directly contribute to its industrial popularity.

Corrosion Resistance

• Exceptional resistance to chloride stress corrosion cracking and sulfide stress cracking (SSC).

• Performs well in H₂S + CO₂ environments, typical in oilfield and subsea operations.

• Resistant to pitting and crevice corrosion in seawater and brine.

Mechanical Strength

• Tensile Strength: 930–1100 MPa

• Yield Strength: 690–760 MPa

• Elongation: 20–30 percent

These mechanical advantages combined with non-magnetic behavior make Inconel 925 an ideal material for critical components under pressure and corrosive attack.

10. Applications Requiring Non-Magnetic Alloys

Because of its stable non-magnetic nature, Inconel 925 is used in applications where magnetic interference could be problematic.

Oil and Gas Industry

• Downhole tubing hangers and packers

• Wellhead and subsurface safety valves

• Couplings, fasteners, and hangers

Marine and Offshore Engineering

• Shafts, pumps, and valves exposed to seawater

• Subsea connectors and structural parts

Instrumentation and Electronics

• Components near magnetic sensors

• Measurement-while-drilling (MWD) equipment

• Non-magnetic housings and brackets

Chemical and Power Generation

• Heat exchangers and reactor vessels

• Acid-handling systems and condensers

In all these sectors, Inconel 925’s non-magnetic, corrosion-resistant, and high-strength properties ensure reliability and long-term service.

11. Advantages of Using Non-Magnetic Inconel 925

• Prevents magnetic interference with sensitive instruments

• Maintains stable performance in magnetic fields

• Resistant to corrosion and high-pressure environments

• High fatigue and tensile strength

• Long service life reduces maintenance costs

• Fully compliant with NACE MR0175 / ISO 15156 for sour gas environments

These advantages make Inconel 925 a preferred choice over traditional stainless steels for high-stress, high-corrosion, and non-magnetic requirements.

12. Testing Magnetic Permeability

Industries often test the magnetic permeability (μr) of alloys like Inconel 925 to ensure compliance.

• Non-Magnetic: μr = 1.00–1.05

• Weakly Magnetic: μr = 1.05–1.10

• Magnetic: μr > 1.10

Inconel 925 typically falls between 1.00 and 1.02, confirming its non-magnetic nature even after aging or machining.

Testing is performed using instruments such as permeability meters or Helmholtz coils to verify that the material meets non-magnetic specifications.

13. Comparison with Magnetic Materials