Inconel 601 Washers Manufacturer & Supplier in India — ASTM B168 / B166 UNS N06601 Plain, Spring, Square and Tab Washers

Why Alloy 601 Washers Outlast Standard Nickel-Chromium Grades in Cyclic Heat

Inconel 601 washers are aluminium-bearing nickel-chromium load-spreading components blanked from ASTM B168 strip or machined from ASTM B166 bar, specified wherever a bolted joint has to survive repeated heating and cooling without the washer scaling away and letting the clamp load go. Unifit Fastener manufactures the complete Alloy 601 range — part of our wider Inconel washers and Inconel fasteners programme — from our Mumbai works.

Also designated Alloy 601, UNS N06601 and Werkstoff Nr. 2.4851, the grade carries 58–63% nickel and 21–25% chromium — but the 1.00–1.70% aluminium is what actually earns the specification. It builds a tenacious alumina sub-scale beneath the usual chromium oxide film, and that second layer is what stops the scale spalling off every time the furnace cools. In a thermally cycled assembly the washer is normally the first component to scale through and let the joint go slack; Alloy 601 is specified precisely to stop that.

We produce plain, spring, square, tab, star, fender, countersunk, sealing and Belleville profiles from M2 to M36, outside diameters 5 mm to 66 mm and thicknesses 0.3 mm to 5 mm, to ASTM, DIN and ISO dimensional standards. Every batch is PMI-verified for aluminium content and released with an EN 10204 3.1 mill test certificate. Contact our engineering team with your profile, size and service temperature for a same-day quotation.

What Are Inconel 601 Washers?

Inconel 601 washers are bearing and locking components blanked from strip or machined from bar in a solid-solution-strengthened nickel-chromium-iron alloy with a deliberate aluminium addition. They sit under bolt heads, nuts and studs in assemblies that spend their working life inside sustained or cycling oxidising heat.

The Metallurgy in Plain Engineering Terms

• Aluminium (1.00–1.70%) is the whole point of the grade. It forms an Alâ‚‚O₃ sub-scale under the chromium oxide layer, giving a dual-oxide structure that adheres through thermal cycling instead of flaking off.
• Chromium (21–25%) — noticeably higher than the 14–17% in Inconel 600 — carries the primary oxidation and sulphidation resistance.
• Nickel (58–63%) provides the austenitic matrix, structural stability and resistance to chloride stress corrosion cracking.
• Iron (balance) keeps the alloy affordable relative to fully nickel-based grades without compromising high-temperature behaviour.
• Low carbon (0.10% max) limits grain-boundary carbide networks that would embrittle the washer after long hot holds.

Why the Washer Is the Component That Fails First

In a hot flanged joint, preload is lost through three mechanisms: thermal expansion mismatch, creep relaxation of the stud, and embedment — the bearing surfaces yielding and bedding in under the head and nut. A washer in the wrong material accelerates all three. Once it scales, its thickness changes and the joint goes slack; once it softens, the head embeds into it. Alloy 601 addresses this because its oxide layer stays put and its structure remains stable at temperatures where austenitic stainless washers have long since scaled through.

Commercial Benefits of Buying From Unifit Fastener

• Matched joint sets — Alloy 601 washers supplied alongside Inconel 601 fasteners, Inconel stud bolts and nickel alloy nuts from compatible heats, so the whole joint expands at one rate and no single component becomes the weak link on the next thermal cycle.
• Custom profiles without tooling drama — tab washers, lock plates, ogee and dock washers and non-standard OD/ID combinations made to drawing.
• Thin-gauge capability — down to 0.3 mm for shim and spacer applications where most suppliers start at 1 mm.
• Documented traceability — heat number recorded, EN 10204 3.1 certificate issued, PMI report on request.
• Low minimum order quantities so maintenance teams can buy genuine replacement counts, not surplus stock.

Complete Inconel 601 Washer Range

Fifteen distinct profiles, all produced in-house from certified Alloy 601 strip or bar. Each entry below states the governing dimensional standard so your drawing office can specify without a phone call.

Related pages: Inconel washers, nickel alloy washers, our general washers manufacturer capability, and the reference guide to types of washers.

Inconel 601 Washer Dimension Charts

DIN 125 A Plain Washer Dimensions (Alloy 601)

All dimensions in millimetres. Form A supplied as standard; Form B (chamfered) available on request.

DIN 127 B Spring Lock Washer Dimensions (Alloy 601)

Inconel 601 Washer Weight Chart

Calculated for DIN 125 A plain washers at the Alloy 601 density of 8.11 g/cm³, using volume = π/4 × (d2² − d1²) × s. Use these figures for costing, freight estimation and bill-of-quantity preparation.

Figures are theoretical and exclude chamfers, deburring loss and dimensional tolerance; actual shipped weights typically fall within 2–3% of these values. Competitor charts stop at M20 — the sizes above that are where furnace and radiant tube assemblies actually consume material.

Temperature Capability: What the Numbers Actually Mean

Published maximum temperatures for Alloy 601 range from 982°C to 1250°C across supplier websites, and they are not all describing the same thing. Three different limits get quoted interchangeably.

For a washer that is purely a bearing and spacing component, the oxidation limit is the governing number, because the failure mode is scaling and thickness loss. For a washer carrying preload in a stack under sustained stress, design to the lower creep-governed figure. If a supplier quotes only one number without saying which, ask.

Spring Washers, Belleville Washers and Preload Retention

A question we are asked constantly and which no competitor page addresses: do spring washers still work at temperature?

Honestly — only partly. A conventional split lock washer to DIN 127 works by elastic spring-back. At sustained high temperature, that stored elastic energy relaxes through creep, and by the time the assembly has been through a few thermal cycles the washer is contributing far less locking effect than it did cold. Alloy 601 relaxes far more slowly than stainless steel, but it is not immune. Three practical options follow from that:

1. Belleville (conical disc) washers to DIN 6796 are the better choice for hot joints. They provide much higher spring rate over a longer deflection range, so proportional relaxation costs you less clamp load. Stack them in series for more travel or in parallel for more force.
2. Tab washers and lock plates to DIN 93 / DIN 463 provide *mechanical* locking rather than elastic locking. They do not relax, because nothing is relying on stored spring energy. For furnace hardware that will not be revisited between campaigns, this is often the most reliable answer.
3. Re-torquing after the first heat cycle remains standard good practice regardless of washer type, and no washer selection eliminates the need for it on a critical joint.

We will advise on the right profile for your joint if you send the assembly drawing and service temperature — it is a five-minute conversation that regularly changes the order.

Inconel 601 vs Inconel 600 Washers

This is the decision most buyers on this page are actually making, so it deserves a direct answer rather than a marketing one.

The short version: 601 for heat and cycling, 600 for chemistry. If your washers are scaling and thinning, move to 601. If they are cracking or being attacked chemically, Inconel 600 is likely the better answer.

Wider Nickel Alloy Washer Selection Grid

Compare with Incoloy 800 / 800HT washers, Hastelloy washers, Monel washers, duplex steel washers, super duplex steel washers and stainless steel washers.

Applications & Industries Served

Further reading: advantages of nickel alloy fasteners and why stainless steel washers are preferred in corrosive environments for the grade below this one.

Our Manufacturing & Quality Process

Step-by-Step Production Route

1. Raw material intake — certified Alloy 601 strip, plate and bar from approved mills, verified against the mill certificate on arrival.
2. Incoming PMI and chemistry check — optical emission spectroscopy confirms Ni, Cr and critically Al before material enters production. Aluminium is the element that defines this grade, and it is the one worth verifying.
3. Blanking or machining — precision blanking and CNC punching from strip for standard profiles; bar-stock turning for large diameters and machined specials.
4. Cold forming — spring, Belleville, wave and tab profiles formed to the required spring rate and geometry.
5. Deburring and tumbling — removes blanking burrs that would otherwise become crack initiation sites or damage the flange face.
6. Solution annealing — restores a stress-free austenitic structure and optimises subsequent oxide-scale formation.
7. Pickling and descaling — removes heat-treatment oxide and leaves a clean surface for the service film to develop.
8. Optional finishing — bright annealing, mechanical polishing to Ra 0.4–0.8 µm, electropolishing or passivation.
9. Inspection — dimensional check, hardness, PMI and high-temperature soak testing where specified.
10. Marking, documentation and packing — heat number recorded, EN 10204 3.1 certificate issued, VCI wrapping and export-grade boxing.

Testing We Perform

Standards, Certifications & Documentation

More context in our fasteners standards reference and the guide to DIN 126 plain washer dimensions.

Documentation Supplied With Every Order

• EN 10204 3.1 mill test certificate with heat number and full chemistry including aluminium
• Dimensional inspection report against the applicable DIN/ISO clause or your drawing
• Mechanical property report for the source strip or bar
• PMI scan report on request
• Packing list, commercial invoice and country-of-origin certificate for export consignments
• Third-party inspection release note where a TPI agency is nominated

Why Buy Inconel 601 Washers From Unifit Fastener

Washers are treated as a commodity by most suppliers, which is exactly why they cause problems. A washer ordered on price alone, from a certificate that does not name the right standard, is the component that quietly determines when your furnace assembly needs opening up again.

Global Supply Footprint

We supply Inconel 601 washers across India — Mumbai, Pune, Ahmedabad, Chennai, Hyderabad, Bangalore, Coimbatore, Jamnagar, Vadodara, Kolkata, Vizag and Pimpri-Chinchwad — and export to the UAE, Saudi Arabia, Qatar, Oman, Kuwait, Bahrain, Jordan, Egypt, Morocco, Algeria, Nigeria, South Africa, Singapore, Malaysia, Thailand, Indonesia, Vietnam, South Korea, Japan, Australia, the United States, Canada, Mexico, Brazil, Peru, the United Kingdom, Germany, Netherlands, Italy and Turkey.

Packing & Dispatch

• Bulk quantities in cartons on palletised loads; thin-gauge washers interleaved to prevent edge damage
• VCI paper and moisture-barrier wrapping for sea freight
• Fumigated wooden crates conforming to ISPM-15 for export
• Heat number, size and profile marked on every package
• Air, sea and courier dispatch with export documentation handled end-to-end

Inconel 601 Washer Price: What Actually Drives Your Quote

Send us the profile, size, quantity, standard and service temperature and you will receive a line-itemised quotation — not a range.

Get Your Inconel 601 Washer Quote in One Working Day

Send us the profile, size, quantity and service temperature — our engineering team will confirm the right washer type and grade before quoting. If a Belleville or tab washer would serve you better than the spring washer you asked for, we will say so.

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