Hastelloy fasteners are a class of high-performance alloy fasteners which find their application in very tough conditions requiring high corrosion resistance, high temperature strength, and high chemical stability. Different grades of hastelloy fasteners include Hastelloy C276 fasteners and Hastelloy C22 fasteners, and find wide application in industries like chemical processing industries, marine, and offshore industries. Hastelloy fasteners are recommended by engineers for use in applications that require very aggressive conditions and where other fasteners fail to perform. We at Jade Alloys manufacture high quality Hastelloy fasteners and other material which is used in different industries according to their usage.
What is Hastelloy?
Hastelloy is a group of super alloys made up of nickel alloys, which are very resistant to corrosion, especially in places where stainless steel does not work. The percentage of nickel in Hastelloy C276 is very high (around 57%), and also the percentage of molybdenum (15-17%) in it is high compared to SS 316 (which has around 2-3% of molybdenum). C-Series alloys are available, which are resistant to both oxidizing and reducing acids, and B-Series alloys (7% to 28% molybdenum) are designed for high reducing conditions. Despite its cost, Hastelloy fasteners are used in critical fastener applications like chemical reactors or offshore systems, with a promise of long-term reliability and performance without incurring severe operational and safety risks due to material failure.
Hastelloy Grades Used in Fasteners
There are 7 Hastelloy grades that have a significant and meaningful frequency in fastener specifications. The vast majority of orders are C276 and C22, while the remaining orders are for more specific corrosion situations. The table below provides a correlation between the grade and the UNS designation, the predominant alloying elements, the outstanding corrosion property, and the most common fastener form.
| Grade | UNS No. | Key Alloying Elements (%) | Standout Corrosion Property | Typical Fastener Form / Use |
| C276 | N10276 | Ni 57 min, Mo 15–17,Cr 14.5–16.5, W 3–4.5,Fe 4–7 | Broadest resistance of any standard alloy: HCl, H_2SO_4, HF, oxidizing/reducing mixed media, and wet chlorine. | Hex bolts, stud bolts, hex nuts, washers, and U-bolts. |
| C22 | N06022 | Ni 56 min, Cr 20–22.5,Mo 12.5–14.5, W 2.5–3.5,Fe 2–6 | Superior oxidizing acid resistance vs. C276 (due to higher Cr); excellent in mixed acid/oxidizing media; superior pitting resistance. | Hex bolts, stud bolts, and nuts; preferred for Flue-Gas Desulfurization (FGD) and chemical plants. |
| B2 | N10665 | Ni 69 min, Mo 26–30, Cr max 1, Fe max 2 | Exceptional resistance to pure HCl and H_2SO_4 at all concentrations/temperatures; near-zero Cr means no oxidizing media resistance. | Stud bolts and hex bolts for pure reducing acid service. |
| B3 | N10675 | Ni 65 min, Mo 28.5,Cr 1–3, Fe max 1.5,Co max 3 | Improved thermal stability over B2; reduced knife-line and heat-affected zone attack; identical reducing acid resistance with lower SCC risk. | Preferred replacement for B2 in new project designs; stud bolts and hex bolts. |
| C4 | N06455 | Ni 65 min, Cr 14–18,Mo 14–17, Ti 0.7,Fe max 3 | Outstanding thermal stability at 650–1,040°C; strong resistance to stress-corrosion cracking (SCC); lower Tungsten (W) than C276. | High-temperature process fasteners; less common than C276. |
| X | N06002 | Ni 47 min, Cr 20.5–23,Mo 8–10, W 0.2–1,Fe 17–20, Co 0.5–2.5 | Outstanding oxidation resistance and high-temperature strength up to 1,200°C. | High-temperature fasteners in furnace, combustion, and gas turbine equipment. |
| C2000 | N06200 | Ni 59 min, Cr 22–24, Mo 15–17, Cu 1.3–1.9, Fe max 3 | Broadest corrosion resistance in the C-series due to Copper (Cu) addition for HCl resistance; superior to C276 in oxidizing halides. | Niche fastener applications; advanced chemical processing lines. |
Hastelloy C276 Fastener Mechanical Properties
The properties listed below apply to Hastelloy C276 bar stock and forgings that are used to make fasteners, as specified in ASTM B574, Hot-Finished and Cold-Drawn Rod and Bar (SB-574) and ASTM B564, Nickel Alloy Forgings (SB-564), adopted into ASME codes. The values apply to the annealed condition, the normal supply condition of fastener stock made of C276.
| Property | Value | Notes |
| Tensile Strength, R_m (min) | 690 MPa (100 ksi) | Minimum limit per ASTM B574; typical production runs range between 760–860 MPa. |
| Yield Strength, R_{p0.2} (min) | 283 MPa (41 ksi) | Minimum limit per ASTM B574; typical values sit around 310–380 MPa. |
| Elongation at break (min) | 40% | Demonstrates excellent ductility; supports highly loaded joints without the risk of brittle sudden failure. |
| Hardness (max) | 100 HRB | Equivalent to approx. 240 HV / 22 HRC. This is significantly softer than Class 10.9 or 12.9 high-tensile alloy steels. |
| Density | 8.89 g/cm³ | Notably heavier than SS 316 (7.99 g/cm³) and alloy steel (7.85 g/cm³); critical for weight-sensitive or aerospace/subsea balancing calculations. |
| Modulus of Elasticity | 205 GPa | Right in line with SS 316; joint compliance and torque-tension calculations can utilize a similar basis. |
| Thermal Expansion Coefficient | 11.2 µm/m·°C (20–100 °C) | Considerably lower than SS 316 (16.0 µm/m·°C). This reduction is crucial when calculating clamping force retention in flanged joints undergoing thermal cycling. |
| Max Service Temperature | ~1,040 °C | Maintains scale and oxidation resistance up to this point, though structural mechanical strength is severely derated above 500°C. |
Hastelloy vs SS 316 vs Inconel 625: When to Choose What?
The most frequent specification situation for engineers is the selection of one of three standard fasteners SS 316, the standard corrosion resistant fastener, Inconel 625, the default high performing fastener of the nickel alloy group, and Hastelloy C276, the specialist reducing-acid and mixed-media solution. The next table makes the direct mapping. See the Inconel alloys guide for a detailed description of Inconel alloys and properties.
| Factor | SS 316 / A4 | Inconel 625 | Hastelloy C276 |
| HCl Resistance | Poor — fails rapidly in concentrated Hydrochloric acid (HCl) even at room temperature. | Moderate — resists dilute HCl; attacked by concentrated HCl at elevated temperatures. | Excellent — resists all concentrations of HCl, including hot, concentrated acid streams. |
| H_2SO_4 Resistance | Limited — handles dilute only; fails rapidly above ~50% concentration. | Good in moderate concentrations; performance is limited in highly concentrated Sulfuric acid. | Excellent across a wide concentration and temperature range. |
| Hydrofluoric Acid (HF) | Not recommended | Moderate | Good — one of the few alloys to offer meaningful industrial HF resistance. |
| Seawater / Chloride Resistance | Susceptible to pitting and crevice corrosion in stagnant seawater; marginal. | Excellent — high Molybdenum (Mo) and Niobium (Nb) content; a preferred choice for subsea and offshore. | Excellent — the combination of Mo + W provides outstanding pitting resistance in seawater. |
| Oxidizing Acid Resistance | Good in dilute Nitric acid (HNO_3); passivates well in oxidizing media. | Good — handles most oxidizing environments well. | Good; note that Hastelloy C22 outperforms C276 in strongly oxidizing environments due to its higher Chromium (Cr) content. |
| Stress Corrosion Cracking (SCC) | Susceptible in hot chloride environments when temperatures climb above ~60°C. | Excellent SCC resistance. | Excellent SCC resistance — fully compliant and suitable for NACE MR0175 sour gas service. |
| Tensile Strength (Annealed) | 515–800 MPa (A4-70 to A4-80) | 930 MPa minimum (per ASTM B446) | 690 MPa minimum (per ASTM B574) |
| Max Service Temp (Corrosion) | ~300°C practical limit | ~980°C oxidizing atmosphere | ~1,040°C oxidizing atmosphere |
| Relative Cost (Fasteners) | Low (Baseline standard) | High (~8–12× SS 316) | High (~6–10× SS 316) |
| Availability (Standard Sizes) | Excellent — widest off-the-shelf stocking worldwide. | Good for standard sizes; larger diameters usually made to order. | Good for C276; variant grades like C22 or the B-series may require custom lead times. |
Hastelloy Fastener Types and Standards
All standard fasteners are available for Hastelloy. The most common forms supplied by Jade Alloys are:
Hex Bolts:
Hex bolts is Fully and partially threaded, metric (ISO 4014/4017) and UNC/UNF inch threads
Stude Bolts:
Stud bolts are the most common type of flanged pressure joint with dimensions to ASME B16.5 and ASME B18.31.2.
Hex Nuts:
Hex nuts: heavy hex (per ASME B18.2.2) for pressure flange service, standard hex (per ISO 4032)
Washers:
Washers are used to spread the loading on softer flange face materials, DIN 125 / ISO 7089 flat washers.
U Bolts
U-bolts, pipe clamps and special forms – made to drawing for pipe clamps and custom assemblies
Applicable material standards
Unlike ASTM A193/A194 for alloy and stainless steel bolting, there is no single ASTM fastener standard that is specific to hastelloy. Hastelloy fasteners are made from bar or forging material according to material standards and the dimension of the fastener is separately standard. The material standards are:
| Standard | Covers | Applicable Grades | Notes |
| ASTM B574 (ASME SB-574) | Hot-finished and cold-drawn nickel-molybdenum-chromium alloy rod and bar stock. | C276 (N10276), C22 (N06022), B2 (N10665), B3 (N10675), C4, C2000 | Primary stock form for machined fasteners. Covers critical chemical composition limits, tensile properties, bulk hardness, and microstructural grain size requirements. |
| ASTM B564 (ASME SB-564) | Nickel alloy forgings. | All Hastelloy grades including C276, C22, B2, B3, X | Typically utilized for large-diameter nuts, custom heavy flange bolts, and forged fastener blanks; demands stricter metallurgical control than standard bar stock. |
| ASTM B619 / B622 | Welded and seamless nickel alloy pipe, sheet, and strip. | C276, C22, B2 | Not directly used for standard fasteners; highly relevant for verifying material chemistry or testing parameters of welded assemblies or components. |
Hastelloy fasteners raw material is also available in bar and plate form. In addition to fabricated components, Hastelloy sheets and plates, and Hastelloy fastener products, Jade Alloys also offers Hastelloy round bars and Hastelloy C276 round bars in various grades.
Key Industries Using Hastelloy Fasteners
Chemical Processing
The HCl and H₂SO₄, acetic acid, chlorinated organic solvents, reactors, heat exchangers, agitator shafts, and piping. C276 is the standard material for flange studs in situations where process streams are combined or where corrosive media are switched in the season. The loss of one unplanned shutdown of a chemical plant is well beyond the premium on Hastelloy compared to SS 316.
Oil & Gas
Where H₂S and CO₂ exist with chloride-bearing brines on wellheads, Christmas tree assemblies, and subsurface safety valves. Hastelloy C276 and C22 fasteners are NACE MR0175 compliant and resist sulphide stress cracking (SSC) and hydrogen-induced cracking (HIC), which cause the failure of alloy steel and standard stainless grades.
Flue Gas Desulfurisation (FGD)
A power plant scrubber system that deals with hot, wet SO₂ and SO₃ in the presence of chlorides and fluorides, one of the most corrosive industrial environments, other than a laboratory. The preferred grade for FGD ductwork fasteners is C22 due to its higher chromium level, which offers greater protection from the oxidising sulphuric acid/chloride mixture that is common in scrubber liquors.
Pharmaceutical & Biotech
In pharmaceutical manufacturing, strong acids and hypochlorite cleaning solutions can cause damage to SS 316 after multiple cleaning cycles. Strong acids and hypochlorite cleaning solutions can cause damage to SS 316 over multiple cleaning cycles, particularly in pharmaceutical manufacturing. Eliminates risk of contamination from corrosion products in reactor internals and vessel nozzles, crucial in a GMP-controlled environment: Hastelloy C276 fasteners.
Marine & Offshore
Subsea wellhead bolting, riser clamps and topside piping on floating production units that are subject to seawater immersion or spray. Excellent resistance to crevice corrosion — a failure mode that makes the use of SS 316 bolts totally unsuitable when immersed in seawater and is suitable for deepwater, high-pressure service.
Waste Treatment & Incineration
The Mixed acidic and oxidising effluents are treated using incinerator gas scrubbers, leachate treatment systems and hazardous waste reactors. The different composition of the media in these environments, which is unpredictable, makes C276 the lower risk specification than optimising for one corrosive agent.
Procurement Checklist for Hastelloy Fasteners
Hastelloy is not a specification. Requesting Hastelloy bolts is the same as requesting stainless Steel bolts and gives a supplier little information. This is a checklist of the minimum data you need to put together for a technically sound order for Hastelloy fasteners in a critical application.
Specify Correct Grade & Standard
Be sure to specify the exact Hastelloy grade, UNS number and ASTM standard (e.g., Hastelloy C276 – UNS N10276 – ASTM B574). The term “Hastelloy bolts” is not specific enough and can result in wrong materials being supplied, since there are very different grades with regard to corrosion resistance.
Mill Test Certificate (MTC) Verification
Ask for a full mill test certificate that details the chemistry, tensile and hardness properties. Pay attention to the presence of essential components such as Ni (57%), Mo (15-17%) and Cr, to ensure the authenticity of the material.
Heat Number Traceability
Use a heat number to trace each fastener to the original material source. This is essential for adherence to ASME, PED and NACE standards particularly for pressure vessels and sour service applications.
Thread & Fastener Specifications
Specify the type of thread (metric or UNC/UNF), the type of bolt (hex bolt/ stud bolt) and the dimensions. If incorrect thread is used, this can cause major assembly failures in critical joints.
Surface Finish & Coating Considerations
Generally, Hastelloy fasteners are provided in a bare or a passivated finish. Do not use zinc or cadmium electroplated coatings, as they may decrease corrosion ability and lead to localized corrosion in harsh environments.
Sourcing Hastelloy C276 or C22 Fasteners?
Jade Alloys is a specialist supplier of Hastelloy C276 and C22 fasteners — hex bolts, stud bolts, nuts, and washers — with full heat traceability and mill test certificates. We supply standard and custom sizes for chemical plant, offshore, and pharmaceutical applications.
