RAYCHIN LIMITED

Expertise Across the Full A286 Fastener Range

Manufacturing Standards for A286 Fasteners

RAYCHIN LIMITED manufactures A286 fasteners to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.

International Standards & Global Designations for A286 Fasteners

To serve clients worldwide, RAYCHIN LIMITED manufactures A286 fasteners from material conforming to the following national and international specifications. This ensures full compliance for projects in the Americas, Europe, Asia, and the Middle East.

UNS S66286 Alloy 660 ASTM A453 AMS 5732 AMS 5737 NACE MR0175 1.4980

Chemical Composition (Weight %) – A286 Superalloy (UNS S66286 / 1.4980)

Our A286 bolts, nuts, screws, washers, stud bolts and threaded rods are produced from melts that strictly conform to the limits below per ASTM A453 / AMS 5731. The high nickel and chromium content provide excellent oxidation resistance, while titanium and aluminum enable precipitation hardening through gamma-prime (γ') phase formation. Molybdenum and vanadium contribute to solid solution strengthening, and boron enhances creep resistance.

Expert note: The combination of titanium and aluminum promotes the formation of Ni₃(Al,Ti) gamma-prime precipitates during aging, which provide A286 with its exceptional high-temperature strength. The addition of boron (0.001-0.010%) significantly improves creep resistance by strengthening grain boundaries. With nickel content of 24-27%, A286 offers excellent resistance to chloride stress corrosion cracking and maintains a stable austenitic structure from cryogenic temperatures up to 700°C.

Complete Mechanical Properties of A286 Fasteners (per ASTM A453)

A286 fasteners are supplied in the solution annealed and precipitation hardened condition (982°C solution treat + 718°C age for 16 hours). ASTM A453 defines multiple classes for different strength levels and size ranges. The data below represent minimum requirements per ASTM A453/A453M.

Tensile Requirements by Class – ASTM A453 Grade 660

Hardness Requirements

Stress Rupture Properties (650°C / 1200°F)

A critical requirement for high-temperature fasteners is stress rupture resistance. Per ASTM A453, Class A, B, and C materials must meet the following:

Note: Class D does not have a mandatory stress rupture requirement but can be supplied with testing upon request. Our in-house testing confirms that Class D materials typically exceed 100 hours at 385 MPa.

Impact Properties (Charpy V-Notch)

A286 maintains excellent impact toughness across a wide temperature range, including cryogenic applications down to -196°C.

Temperature-Dependent Yield Strength

The following table shows minimum yield strength (0.2% offset) at elevated temperatures for A286 in the fully heat-treated condition.

Thermal Expansion Advantage of A286 Fasteners

A286 is specifically designed for bolting austenitic stainless steel flanges and components operating at elevated temperatures. Its thermal expansion coefficient closely matches that of 304/316 stainless steels, preventing loss of bolt preload during thermal cycling.

This expansion match is critical for maintaining gasket stress in high-temperature applications such as refinery heat exchangers, turbine casings, and power generation equipment. Standard alloy steel bolts (B7, B16) expand less than the flange, leading to preload loss and potential leakage. A286 eliminates this mismatch.

API 6A & NACE MR0175 Compliance

A286 fasteners are widely used in oil and gas applications requiring sour service resistance. Per API 6A and API 20F, A286 Grade 660 Class D is approved for H₂S service with maximum hardness of 35 HRC.

Heat Treatment & Microstructural Stability

Optimal mechanical properties in A286 are achieved through a two-step heat treatment:

• Solution Annealing: 980°C (1800°F) for 1 hour, oil quench or water quench. This dissolves carbides and prepares the matrix for precipitation hardening.
• Aging (Precipitation Hardening): 718°C (1325°F) for 16 hours, air cool. This forms coherent γ' (gamma-prime) precipitates [Ni₃(Al,Ti)] that provide high-temperature strength.

Metallurgical studies show that aging at 730°C accelerates precipitation kinetics but can lead to overaging and formation of η (eta) phase (Ni₃Ti), which degrades mechanical properties. Our controlled aging at 718°C ensures optimal γ' formation while avoiding η phase precipitation, maximizing creep resistance and long-term stability.

Physical Properties of A286

Corrosion Resistance of A286 Fasteners

While A286 is primarily selected for high-temperature strength, it also offers good corrosion resistance in many environments due to its high chromium (14-16%) and nickel (24-27%) content. The alloy exhibits excellent oxidation resistance up to 700°C continuous service and 815°C intermittent service.

Oxidation and Scaling Resistance

The chromium content provides excellent resistance to oxidation and scaling. A286 fasteners form a protective Cr₂O₃ scale that prevents further oxidation at elevated temperatures. This protective layer regenerates rapidly if damaged, provided sufficient chromium is available.

Corrosion in Other Environments

Critical Corrosion Considerations for Fasteners

• Oxidation Resistance: A286 can be used continuously up to 700°C (1292°F) in air without significant scaling. For intermittent service, temperatures up to 815°C (1500°F) are acceptable.
• NACE MR0175 Compliance: A286 is qualified for sour service (sulfide stress cracking resistance) in oilfield equipment per NACE MR0175/ISO 15156. Class D with maximum hardness 35 HRC is preferred for sour applications.
• Temperature Limitations: Maximum service temperature for continuous corrosion applications is approximately 700°C. Beyond this, consider nickel-based alloys such as Inconel 718.
• Galvanic Corrosion: When paired with lower-grade materials, galvanic corrosion should be considered. A286 is cathodic to most stainless steels but compatible with nickel-based alloys.
• Non-Magnetic Property: A286 is essentially non-magnetic (permeability ≈1.01), making it suitable for applications requiring non-magnetic fasteners such as MRI equipment, sensitive instrumentation, and electrical applications.
• Surface Treatments: Available coatings include Xylan 1070/1014/1400, SermaGard 1105/1280, Dacromet 320/500, and silver plating for anti-galling at high temperatures.

High-Temperature Engineering Note: For critical applications in aggressive environments, RAYCHIN LIMITED can provide passivation, specialized coatings, or recommend optimal heat treatment conditions. Third-party corrosion testing per ASTM G31, G48, or G61 available upon request. NACE MR0175 compliant A286 fasteners available in Class D condition with certified hardness ≤ 35 HRC. A286 offers a cost-effective balance of high-temperature strength and corrosion resistance – approximately 60-70% the cost of nickel-based alloys like Inconel 718.

Why RAYCHIN LIMITED – The A286 Fastener Authority