ASTM B637 / ASME SB637 Certified Manufacturing
Inconel X750 Washers (UNS N07750) maintain full clamping load and dimensional stability at continuous service temperatures up to 816°C — a performance threshold that eliminates austenitic stainless steel alternatives in aerospace bolted joints, nuclear pressure vessel closures, and sour-service oil and gas flanges. Unifit Fastener manufactures ASTM B637-certified Inconel X750 Washers in 9 types — from M02 flat to M33 dome-tooth and spherical — with in-house precipitation hardening to Type 1, 2C, and 3 temper conditions.
Our washers meet the requirements of ASTM B637 and ASME SB637, which guarantees dimensional accuracy, excellent mechanical strength, and the highest resistance to the environment. Our range of sizes from M02 to M33 and lengths from 3 mm to 200 mm includes every engineering specification, ranging from flat, lock, sealing, spring, star, and tab washers. Supported by ISO 9001:2015 certification, traceable raw materials, and a thorough quality assurance system.
Unifit Fastener is the brand for washers that will outlast and outperform in the toughest environments.
Get a Free Quote for Inconel X750 WashersInconel X750 Washers are high-performance fastening components manufactured from a precipitation-hardened nickel-chromium superalloy, designated as UNS N07750 and Werkstoff Nr. 2.4669. The alloy derives its exceptional properties from carefully controlled additions of titanium, aluminium, niobium, and iron to a nickel-chromium base matrix.
These washers function as load-distributing elements used beneath bolt heads and nuts in bolted assemblies. What differentiates Inconel X750 washers from standard stainless steel or carbon steel equivalents is their ability to maintain structural integrity and dimensional stability across extreme temperature ranges — from cryogenic conditions to over 800°C — while simultaneously resisting oxidation, chemical attack, and stress-corrosion cracking.
The precipitation-hardening treatment (solution annealing followed by aging) transforms the alloy's microstructure, producing the gamma-prime (γ') phase that delivers the alloy's signature combination of high tensile strength, creep resistance, and fatigue resistance — properties critical in rotating machinery, pressure vessels, and structural aerospace applications.
| Specification Parameter | Details |
| Material Grade | Inconel X-750 (UNS N07750 / WNR 2.4669) |
| Standard | ASTM B637 / ASME SB637 |
| Dimensions | DIN 125, DIN 127, ISO 7089, ISO 7090, ASME B18.22.1 |
| Nominal Size Range | M2 to M33 | Custom sizes available |
| Inside Diameter (ID) | As per applicable standard |
| Outside Diameter (OD) | As per applicable standard |
| Thickness | As per DIN/ISO/ASME standard or customer drawing |
| Manufacturing Type | Cold Forged, Hot Forged, Bar Stock Machined, CNC Machined |
| Surface Finish | Black Oxide, Passivated, Polished, As-Machined |
| Service Temperature | Cryogenic to 1500°F (816°C) |
| Standard | UNS Number | DIN / WNR Number |
| Inconel X-750 | N07750 | 2.4669 |
| Al | C | Cr | Co | Cu | Fe | Mn | Nb | Ni | Ti | S | Si |
| 0.40-1.0 | 0.08 max | 14.0-17.0 | 1.00 max | 0.50 max | 5.0-9.0 | 1.00 max | 0.70-1.20 | 70.0 min | 2.25-2.75 | 0.01 max | 0.50 max |
Note: All values are in weight percentage (wt%). Nickel content is the balance element. Minor additions of titanium and aluminium enable the precipitation of the gamma-prime strengthening phase during aging heat treatment.
| Property | Value (Metric) | Value (Imperial) |
| Ultimate Tensile Strength | 1250 MPa | 181,000 psi |
| 0.2% Yield Strength | 850 MPa | 123,000 psi |
| Elongation (%) | 30% | 30% |
| Rockwell Hardness (Type 2C) | 32-40 Rc | 32-40 Rc |
| Density | 8.28 g/cm³ | 0.299 lb/in³ |
| Melting Range | 1393-1427°C | 2540-2600°F |
| Type | Heat Treatment Process | Tensile Strength (psi) |
| Type 1 | Solution at 2100°F (1149°C) + stabilize + precipitation harden | 140,000 (965 MPa) |
| Type 2C | Solution at 1800°F (982°C) + precipitation harden | 170,000 (1170 MPa) |
| Type 3 | Solution anneal at 2000°F (1093°C) + precipitation harden | 160,000-185,000 (1103-1276 MPa) |
Inconel X750 Washers from Unifit Fastener are engineered to perform in the world's most demanding environments. Their unique combination of high-temperature strength and chemical inertness makes them indispensable across the following industries:
| Property | Inconel X750 | SS 316L | Inconel 625 | Hastelloy C276 |
| Max Service Temp. | 816°C | 870°C* | 980°C | 1037°C |
| Tensile Strength | 1250 MPa | 515 MPa | 930 MPa | 790 MPa |
| Yield Strength | 850 MPa | 205 MPa | 517 MPa | 355 MPa |
| Pitting Resistance | Excellent | Good | Excellent | Superior |
| Precipitation Hardened | Yes | No | No | No |
| Aerospace Approved | Yes | Limited | Yes | Yes |
| Relative Cost | Medium-High | Low | High | High |
SS 316L retains approximately 50% of room-temperature yield strength at 500°C (approx. 100 MPa vs 205 MPa) and is generally not specified above 550°C for structural bolting
Our Inconel X750 washers are produced through a rigorous multi-stage manufacturing process that ensures every component meets or exceeds the specified mechanical and dimensional requirements:
Certified Inconel X750 bar stock and coil is sourced from approved mill partners. Every heat is verified against mill test reports and subjected to incoming PMI before release to production.
Depending on washer type and size, forming is carried out by cold forging (small sizes up to M20), hot forging (larger sizes), or precision bar stock machining on CNC lathes and mills for complex geometries.
Solution annealing and precipitation hardening are performed in AMS 2750-compliant temperature-controlled furnaces. Heat-treatment cycles follow ASTM B637 Table 1 requirements for the specified ASTM B637 condition. Process parameters are monitored and recorded to ensure conformance with customer and material specification requirements.
Post-heat treatment, washers undergo descaling, passivation, or polishing per the customer's surface finish specification. Electropolishing is available for ultra-clean service applications.
100% dimensional inspection, hardness testing on sampled lots, and review against the approved inspection test plan (ITP) precede packing. Each shipment is accompanied by a complete documentation package including MTRs, test reports, and dimensional certificates.
Unifit Fastener manufactures Inconel X750 Washers from M02 to M33 in standard metric sizes, with thickness/length from 3mm to 200mm. Custom sizes beyond this range can be manufactured to customer drawings and specifications.
Yes. Inconel X750 maintains excellent toughness and ductility at cryogenic temperatures, making it suitable for LNG (liquefied natural gas) equipment, aerospace fuel system applications, and other sub-zero service environments.
Inconel X750 Washers can be used in continuous service up to approximately 816°C (1500°F). Above this temperature, oxidation resistance diminishes. For applications above 900°C, Inconel 625 or Hastelloy C276 alternatives should be evaluated.
Yes. Unifit Fastener provides complete material traceability documentation with every shipment, including certified mill test reports (chemical and mechanical), heat treatment certificates, dimensional inspection reports, and third-party test reports where specified by the customer's purchase order.
Standard sizes from M02 to M20 are typically available from stock or can be produced within 7-15 working days. Larger sizes, custom geometries, or high-volume orders require 15-30 working days depending on heat treatment scheduling. Express production is available on request.