HASTELLOY C-4 FASTENERS — DATASHEET, CHEMICAL COMPOSITION, MECHANICAL PROPERTIES & SUPPLY

Ananka Fasteners is a premier manufacturer and global exporter of Hastelloy C-4 Fasteners (UNS N06455 / W.Nr. 2.4610), a pinnacle of microstructural engineering within the nickel-chromium-molybdenum (Ni-Cr-Mo) superalloy family. The "C-type" Hastelloy family is universally recognized for its broad-spectrum resistance to highly aggressive, mixed chemical environments. However, Hastelloy C-4 distinguishes itself by maintaining exceptional ductility and profound corrosion resistance even after prolonged high-temperature aging.

The defining engineering breakthrough of UNS N06455 is its unprecedented microstructural stability. By intentionally removing tungsten, maintaining ultra-low carbon and silicon levels, and adding titanium as a micro-stabilizer, C-4 radically suppresses the precipitation of deleterious intermetallic phases (like μ-phase and M₆C carbides) in the 649°C to 1093°C (1200°F to 2000°F) range. This prevents sensitization, allowing fasteners to be deployed in continuous high-temperature service or in the as-welded condition without fear of catastrophic intergranular corrosion.

Every Hastelloy C-4 fastener manufactured by Ananka is produced utilizing precision CNC machining, optimized carbide/ceramic tooling, and controlled hot or cold forging. All supplies are backed by EN 10204 Type 3.1 Material Test Certificates, full traceability, and rigorous solution annealing to guarantee absolute microstructural purity. We supply mission-critical fastening systems to the chemical processing, nuclear energy, and petrochemical refining sectors worldwide.

Every lot of Hastelloy C-4 fasteners shipped by Ananka is accompanied by a highly detailed EN 10204 Type 3.1 Manufacturer Test Certificate (MTC), ensuring absolute metallurgical pedigree traceable back to the originating vacuum-induction melt.

Each MTC documents:

• Actual chemical analysis confirming ultra-low Carbon/Silicon limits and absence of Tungsten.
• Complete mechanical tests (ASTM E8/E8M) for yield, ultimate tensile strength, and elongation.
• Nut proof load testing data per ASTM F467.
• Verification of solution annealing heat treatment (typically 1066°C) and rapid quenching.

The alloy balances high concentrations of matrix-forming elements (Ni-Cr-Mo) while strictly limiting interstitial impurities to optimize the balance between high-temperature mechanical strength and ubiquitous corrosion resistance.

At ambient temperatures, Hastelloy C-4 behaves as a highly ductile, tough material with a high modulus of elasticity, ensuring it behaves predictably within the linear elastic region during precise torque-to-yield joint tightening procedures.

High-Temperature Mechanical Degradation

For design engineers calculating torque-to-tension relationships in high-temperature environments, compensating for the drop in Yield Strength and Elastic Modulus is paramount to prevent permanent joint relaxation. The 0.2% Yield Strength typically drops from ≥ 305 MPa at 20°C to approximately 215 MPa at 300°C (572°F), and 205 MPa at 400°C (752°F).

Hastelloy C-4 provides robust defense mechanisms against multiple forms of complex chemical attack, making it the absolute requisite choice when fasteners operate continuously above 650°C or require welding.

• Reducing Acids: The 16% molybdenum content provides a "quantum improvement" over standard austenitic stainless steels in handling aggressive non-oxidizing acids, particularly hydrochloric (HCl) and sulfuric (H₂SO₄) acids.
• Oxidizing Media: The 16% chromium content maintains a passive oxide layer against oxidizing media (such as nitric acid and wet chlorine), yielding highly acceptable corrosion rates.
• Chloride Stress Corrosion Cracking (CSCC): Because the bulk matrix is nickel-based (65% Ni), C-4 is virtually immune to CSCC, a pervasive failure mode in stressed stainless steel fasteners in warm, chloride-bearing aqueous environments.
• Nuclear & Chemical Processing: Mandated in environments where low-cobalt requirements and extreme microstructural stability are required to prevent radioactive leaks or catastrophic failure of pressure vessels and heat exchangers.

• Hastelloy C-4 Bolts: Heavy hex and socket head configurations complying with ASME B18.2.1 dimensions.
• Hastelloy C-4 Nuts: Proof-stress tested nuts per ASTM F467 ensuring internal threads do not shear under massive vessel pressures.
• Hastelloy C-4 Washers: Flat and spring washers for critical load distribution in high-temperature joints.
• Hastelloy C-4 Studs: Uncompromising standard for extreme-environment flanged connections.

Hastelloy C-4 is notoriously difficult to machine due to high shear strength and a profound propensity for rapid work-hardening. Precise machining parameters are required to prevent catastrophic tool failure.

• Machining Parameters: Standard HSS is ineffective. Coated carbides (e.g., TiAlN) or ceramics must be used. Continuous, aggressive feeds (e.g., 0.005–0.010 in/rev) are critical to ensure the tool cuts beneath the work-hardened layer created by the previous pass.
• Thread Rolling: Highly preferred over cutting. Thread rolling plastically deforms the blank, aligning grain flow parallel to the thread roots, significantly enhancing fatigue life and galling resistance.
• Galling Mitigation: Bare nickel alloy threads are highly susceptible to galling under high torque. Dry-film boundary lubricants (PTFE, Xylan) or advanced anti-seize pastes are mandatory to stabilize the friction coefficient (≈ 0.15) and prevent cold welding during assembly.

• Advanced CNC Machining: We utilize state-of-the-art coated carbide and ceramic tooling with High-Pressure Coolant (1000-3000 psi) to overcome C-4's extreme work-hardening rate, guaranteeing flawless dimensional tolerances without damaging the substrate.
• Strict Thermal Protocols: All hot-forged bolts are meticulously solution annealed at 1066°C and rapidly water-quenched to freeze the single-phase solid solution, ensuring maximum corrosion resistance.
• Thread Rolling Superiority: We roll-form threads whenever viable, providing continuous grain flow and compressive root stresses that vastly outperform cut threads in fatigue applications.
• 100% Traceability: Per ASTM F468, all C-4 fasteners are permanently stamped with our manufacturer symbol and proper alloy markings, verified by handheld XRF (PMI) prior to dispatch.