UNS N06601 / DIN 2.4851 | ASTM B166, ASTM B168, ASTM F2281 | M2 to M33
Inconel 601 washers are the engineering solution of choice when ordinary fasteners fail due to extreme temperatures or aggressive corrosive environments. They have a solid-solution nickel-chromium-iron (Ni-Cr-Fe) alloy with a high content of aluminum and provide outstanding oxidation and thermal degradation resistance to 1,250°C (2282°F) and are essential in the petrochemical, aerospace, power generation, and furnace equipment industries. We produce and supply washers (UNS N06601 / DIN 2.4851) to ASTM B166, ASTM B168, and ASTM F2281 standards for your most critical applications at Unifit Fastener. Our Inconel 601 washers come in a range of shapes and sizes, including flat washers, spring washers, lock washers, split washers, star washers, tab washers, countersunk washers, spherical washers, dome tooth washers, and custom washers, from M2 to M33 (3 mm to 200 mm), with full mill test certificates and third-party inspection support. Unifit Fasteners offer precision, reliability, and compliance in every order, whether you're sourcing for domestic projects or for international exports.
Request a Quote| Parameter | Details |
| Material | Inconel 601 (UNS N06601 / WNR 2.4851) |
| Manufacturing Standards | ASTM B166, ASTM B168, ASTM F2281, ASME |
| Dimensional Standards | DIN, ASTM, ASME, BS, IS, JIS and all International Standards |
| Size Range | M2 to M33 | 3 mm to 200 mm | Custom Sizes Available |
| Washer Types | Flat, Plain, Spring, Lock, Split, Star, Tab, Countersunk, Spherical, Dome Tooth, Round, Square, Sealing, Slot, Punched, Fender, Belleville, Wave, Wedge Lock, Dock |
| Max. Service Temperature | 1,250°C (2,282°F) continuous oxidizing atmosphere |
| Supply Condition | Annealed (standard); solution-treated on request |
| Origin | Made in India — exported worldwide |
Inconel 601 is a high-performance Nickel-Chromium-Iron superalloy distinguished by its deliberate aluminium addition (1.0–1.7%). This aluminium content is the key driver of the alloy's exceptional oxidation resistance: when exposed to high temperatures, aluminium reacts with oxygen to form a tightly adherent, self-repairing alumina (Al2O3) scale on the surface that acts as a diffusion barrier against further oxidation — even under severe thermal cycling conditions.
Unlike conventional stainless steels or even Inconel 600, Inconel 601 maintains its structural integrity and surface quality in carburizing, nitriding, and oxidizing atmospheres — making it the preferred washer alloy for high-temperature furnace hardware, thermal processing equipment, and aerospace propulsion components.
| Element | Ni | Cr | Fe | Al | C | Mn | Si | S |
| Inconel 601 | 58.0–63.0% | 21.0–25.0% | Balance | 1.0–1.7% | 0.10 max | 1.0 max | 0.5 max | 0.015 max |
| Property | Density | Melting Range | Tensile Strength | Yield Strength (0.2% Offset) | Elongation | Hardness |
| Inconel 601 | 8.1 g/cm³ | 1,360–1,411°C (2,480–2,571°F) | Min. 80,000 psi (550 MPa) | Min. 30,000 psi (205 MPa) | Min. 30% | 65–85 HRB (Rockwell B) |
Values may vary with specific heat treatment or temper condition
| Standard | Werkstoff Nr. | UNS | JIS | GOST | AFNOR | EN |
| Inconel 601 | 2.4851 | N06601 | NCF 601 | XH60BT | NC23FeA | NiCr23Fe |
Unifit Fastener manufactures the widest range of Inconel 601 washer configurations to cover every engineering requirement — from basic load distribution to specialized vibration dampening and thermal sealing.
| Standard Types | Specialty Types | Custom / Industry Types |
| Flat Washer (Plain Washer) | Star Washer (Internal/External Tooth) | Bearing Lock Washer |
| Spring Washer | Tab Washer | Wedge Lock Washer |
| Lock Washer | Sealing Washer | Dock Washer |
| Split Lock Washer | Countersunk Washer | Punched Washer |
| Square Washer | Dome Tooth Washer | Fender Washer |
| Round Washer | Slot Washer | Belleville Washer |
| Machine Washer | Spherical Washer | Wave Washer |
| Nominal Thread Size | Hole Inner Diameter (mm) | Outside Diameter (mm) | Nominal Thickness (mm) |
| M6 | 6.40 | 12.00 | 1.60 |
| M8 | 8.40 | 16.00 | 1.60 |
| M10 | 10.50 | 20.00 | 2.00 |
| M12 | 13.00 | 24.00 | 2.50 |
| M14 | 15.00 | 28.00 | 2.50 |
| M16 | 17.00 | 30.00 | 3.00 |
| M20 | 21.00 | 37.00 | 3.00 |
| M24 | 25.00 | 44.00 | 4.00 |
| M30 | 31.00 | 56.00 | 4.00 |
| Nominal Size | Inside Diameter Min/Max | Outside Diameter Min/Max | Thickness Min/Max |
| 1/4" | 0.281 / 0.313 | 0.593 / 0.657 | 0.051 / 0.080 |
| 5/16" | 0.344 / 0.376 | 0.656 / 0.720 | 0.051 / 0.080 |
| 3/8" | 0.406 / 0.438 | 0.781 / 0.845 | 0.051 / 0.080 |
| 1/2" | 0.531 / 0.563 | 1.031 / 1.095 | 0.097 / 0.177 |
| 5/8" | 0.688 / 0.720 | 1.281 / 1.345 | 0.122 / 0.177 |
| 3/4" | 0.813 / 0.845 | 1.436 / 1.500 | 0.122 / 0.177 |
| 7/8" | 0.938 / 0.970 | 1.718 / 1.782 | 0.136 / 0.177 |
| 1" | 1.063 / 1.126 | 1.937 / 2.063 | 0.136 / 0.177 |
What makes Inconel 601 washers the superior choice across demanding applications?
| Feature | Engineering Benefit |
| Outstanding Oxidation Resistance | Aluminium-enriched surface oxide layer (Al2O3) self-seals under repeated thermal cycling, preventing scaling and surface degradation up to 1,250°C. |
| Thermal Stability | Retains mechanical properties and dimensional integrity across a wide temperature range — from cryogenic conditions (−196°C) to extreme heat — without creep or deformation. |
| Resistance to Caustic & Alkali Environments | High nickel content provides outstanding immunity to caustic soda, alkalis, and neutral salt environments, preventing localized pitting and stress corrosion cracking. |
| Carburization & Nitriding Resistance | Performs reliably in heat treatment atmospheres where conventional steel and stainless fasteners fail due to carbon or nitrogen pick-up. |
| Cold Welding Prevention | Smooth, controlled bearing surface reduces friction and galling under nut rotation — critical for thread integrity in high-torque and high-temperature assemblies. |
| Excellent Clamping Load Distribution | Distributes bolt clamping forces over a wider flange area, preventing localized crush or embedding — especially important in soft or composite mating surfaces. |
| Vibration & Fatigue Resistance | Spring and helical split variants (DIN 127) provide strong frictional resistance against loosening under heavy mechanical vibration, as found in turbomachinery and aerospace structures. |
The aluminium-modified nickel superalloy composition of Inconel 601 makes these washers the fastening component of choice across the most demanding global industries:
| Industry / Sector | Typical Applications |
| Petrochemical & Refining | Reactor vessels, catalytic crackers, heat exchangers, high-temperature piping flanges, hydrocracker bolt assemblies |
| Aerospace & Defence | Jet engine casing joints, exhaust system flanges, thermal barrier structures, satellite hardware |
| Power Generation | Gas turbine hot sections, steam boiler flanges, nuclear plant ancillary hardware, geothermal equipment |
| Industrial Furnace & Heat Treatment | Furnace door fittings, radiant tubes, muffles, retorts, carburizing and nitriding atmosphere equipment |
| Chemical Processing | Chlorination, fluorination, oxidation reactors, caustic soda production vessels, sulfuric acid concentrators |
| Electronics & Semiconductor | Diffusion furnaces, CVD/PVD equipment, high-temperature support fixtures, lead wire terminals |
| Marine & Offshore | Subsea connector assemblies, offshore rig flanges, seawater desalination plant fittings |
| Food & Pharmaceutical | High-temperature sterilization equipment, autoclave hardware, pharmaceutical reactor seals |
Every Inconel 601 washer from Unifit Fastener passes through a rigorous multi-stage production and quality control process — ensuring dimensional accuracy, metallurgical integrity, and performance under real-world conditions.
| Standard / Certification | Scope |
| ASTM B166 / B168 | Rod, Bar, Plate, Sheet, Strip of Inconel 601 (UNS N06601) |
| ASTM F2281 | Type III, Class A stainless steel and nickel alloy washers |
| ISO 9001:2015 | Quality Management System for manufacturing and supply |
| EN 10204 / 3.1 MTC | Mill Test Certificate with third-party inspection support (SGS, BV, TÜV, DNV) |
| PED / NACE MR0175 | Pressure Equipment Directive and sour service environment compliance on request |
| DIN / BS / JIS Standards | Dimensional compliance with all major international washer standards |
Not all high-temperature alloys are equal. Here is how Inconel 601 compares to the most commonly specified alternatives — helping you make the most informed material selection for your project:
| Property | Inconel 601 | Inconel 600 | Inconel 625 | Incoloy 800HT | SS 310 | SS 316L |
| Max. Service Temp. | 1,250°C | 1,175°C | 1,000°C | 1,100°C | 1,050°C | 870°C |
| Oxidation Resistance | Excellent | Very Good | Good | Good | Good | Fair |
| Caustic/Alkali Resistance | Excellent | Excellent | Good | Good | Fair | Good |
| Al-enhanced Scale Resist. | Yes (Al2O3) | No | No | Partial | No | No |
| Thermal Cycling Resistance | Outstanding | Good | Very Good | Good | Fair | Fair |
| Relative Cost | Moderate–High | Moderate | High | Moderate–High | Low | Low |
| Best For | Furnaces, Petrochemical, Aerospace | Chemical, Aerospace | Marine, Cryogenic | Boilers, Heat Treat | High-Temp Furnaces | General Corrosion |
Inconel 601 is widely used in applications requiring excellent oxidation resistance and high-temperature strength. It is commonly used in furnace components, heat treatment equipment, petrochemical processing plants, thermal processing systems, aerospace components, and power generation industries.
The primary difference between Inconel 600 and Inconel 601 is the addition of aluminum in Inconel 601. This aluminum content significantly improves oxidation resistance at elevated temperatures. While both alloys offer excellent corrosion resistance, Inconel 601 performs better in high-temperature environments, whereas Inconel 600 is preferred for general corrosion and heat-resistant applications.
Alloy 602 contains higher levels of chromium and aluminum than Alloy 601, providing superior oxidation resistance, carburization resistance, and high-temperature strength. Alloy 602 is typically selected for more extreme thermal environments, while Alloy 601 offers an excellent balance of performance and cost for many industrial heating applications.
Inconel is generally harder and stronger than most standard stainless steel grades, particularly at elevated temperatures. It retains its mechanical properties under extreme heat and corrosive conditions where conventional stainless steels may lose strength or deform, making Inconel the preferred choice for demanding industrial applications.
Pricing varies based on washer type, size, quantity, surface condition, and certification requirements. As a direct manufacturer, Unifit Fastener offers competitive ex-factory pricing without trader markups. Request a free quote online or contact our sales team with your specifications for a tailored price list.
Ready to source precision Inconel 601 Washers for your next project? Unifit Fastener is your trusted manufacturing partner — combining metallurgical expertise, ISO-certified production, and a global export network to deliver exactly what your application demands.