Extreme temperature environments create unique challenges for fastener selection. Whether designing for automotive underhood components experiencing 300°F heat cycles, aerospace systems operating at cryogenic temperatures below -300°F, or industrial equipment exposed to furnace conditions exceeding 2000°F, proper material selection is critical for safety, reliability, and performance. Here’s what engineers need to know when specifying fasteners for extreme temperature applications.
Understanding Temperature-Related Failure Modes
Before selecting materials, understanding how temperature affects fastener performance is essential. Extreme temperatures introduce several failure mechanisms that don’t occur at ambient conditions.
High-Temperature Challenges
Oxidation and Corrosion: Heat accelerates oxidation, causing surface degradation and weakening of the fastener. This occurs well below melting temperatures and is one of the most common high-temperature failure modes.
Thermal Expansion and Contraction: High temperatures cause metal fasteners to expand, increasing pressure on surrounding materials. When the metal cools, fasteners contract and loosen. This cyclical stress is particularly problematic in machinery that runs hot but cools when not in use.
Stress Relaxation: A thermochemical reaction that occurs in high-temperature environments where elastic strain slowly becomes plastic strain, creating a reduction in contact force. This phenomenon results in lower vibration resistance, reduced reliability, and less normal force.
Creep Failure: Deformation and buckling that material experiences under constant load, more common in high-temperature settings. Creep affects the fastener’s structural integrity over time, leading to dimensional changes and eventual failure.
Material Strength Loss: Metal weakens and becomes more ductile at high temperatures. While tensile strength increases for some materials, this comes with tradeoffs in other properties.
Low-Temperature Challenges
Brittle Fracture: The ductile-to-brittle transition temperature (DBTT) is the temperature below which a material shifts from ductile behavior (deforms before breaking) to brittle behavior (breaks suddenly without warning). Many common steels become dangerously brittle at cryogenic temperatures.
Reduced Ductility: While tensile strength often increases at low temperatures for some metals, this strength increase can come with significant loss of ductility, leading to brittleness and high risk of sudden fracture.
Phase Transformations: Certain stainless steels that are stable at room temperature can undergo metallurgical phase changes at cryogenic temperatures, transforming from face-centered cubic (FCC) to body-centered cubic (BCC) structure, impairing ductility and toughness.
Thermal Contraction: All materials experience dimensional changes when cooled to low temperatures. This thermal contraction (typically a few tenths of a percent change in volume) can affect joint integrity and preload.
Critical Selection Criteria
When specifying fasteners for extreme temperatures, evaluate these factors:
Operating Temperature Range: Determine the average temperature exposure, peak temperatures, and temperature cycling frequency. Intermittent exposure to 300°F differs dramatically from continuous operation at that temperature.
Duration at Extreme Temperatures: Short-term exposure allows broader material choices than sustained operation. Materials that perform adequately for brief temperature spikes may fail under prolonged exposure.
Environmental Factors: Consider exposure to corrosive chemicals, oxidizing atmospheres, vacuum conditions, or humidity. These factors interact with temperature to accelerate degradation.
Mechanical Loading: Determine if fasteners experience vibration, shock, cyclic loading, or static loads. Combined thermal and mechanical stresses require more robust material selection.
Assembly Requirements: Consider if the assembly requires disassembly for maintenance. Some high-temperature materials become difficult to remove after thermal cycling.
High-Temperature Fastener Materials
Stainless Steel Alloys (Up to 1300°F)
Grades 304 and 316: Austenitic stainless steels perform well up to approximately 800°C (1472°F) with strong corrosion resistance. Ideal for humid heat or acidic exposure in petrochemical pipelines, exhaust systems, and steam boilers.
Grades 309 and 310: The most heat-resistant stainless steels, followed closely by Alloy 330. Grade 310 offers extreme high-temperature oxidation resistance up to 2000°F and cannot be transformed at cryogenic temperatures, making it suitable for applications experiencing wide temperature swings.
Grade 630 (17-4 PH): A martensitic precipitation-hardening stainless steel offering excellent hardness, strength, and ductility for high-temperature fastening. Superior vibration damping compared to austenitic grades.
A-286 (Alloy 660): A stainless steel containing iron, nickel, and chromium with relatively high nickel content. Often used for high heat-resistant bolts and washers. Usable up to 1300°F continuously.
Nickel-Based Superalloys (Up to 2000°F)
Inconel 600: Nickel and chromium alloy very resistant to corrosive elements. The vast majority of Inconel types are oxidation resistant and retain structural integrity at high temperatures.
Inconel 601: Similar to Inconel 600 but with addition of molybdenum, enabling exceptional performance even in extremely high temperatures.
Inconel 625 and 718: Inconel 718 offers outstanding strength and corrosion resistance with maximum tensile strength up to 210 ksi. Both grades are extensively used in aerospace gas turbines for rotating and non-rotating parts.
Waspaloy: A nickel-based superalloy known for high strength and resistance to oxidation, often used in aerospace applications.
Alloy 330: Provides outstanding resistance to carburizing and oxidizing atmospheres caused by extremely high temperatures. Excellent choice for applications alternating between extreme temperatures.
Refractory Metals (Up to 3600°F)
Molybdenum: Incredibly high melting point (4730°F) making it very stable and strong at high temperatures. However, must not be exposed to oxygen at temperatures above 500°F as it oxidizes rapidly and can vaporize.
Tantalum: A refractory metal with usable temperature limit of 3600°F. Best known for corrosion resistance but often used for high-temperature stability and inertness in semiconductor processing. Available as commercially pure tantalum and tantalum 2.5% tungsten.
Note: Refractory metals are generally required for vacuum furnaces where temperatures exceed 2000-3000°F, as they must operate in oxygen-free environments at elevated temperatures.
Ceramic Materials (Up to 4000°F)
Alumina and Zirconia: The ultimate high-temperature fastener materials, capable of operation well beyond 2000°C. Excellent electrical insulation properties, high hardness, and wear resistance.
Limitations: Ceramic fasteners have mechanical drawbacks including limited strength and brittleness. They lack the ductility and fracture toughness of metal alloys and can crack or break if subjected to vibration or shock.
High-Temperature Polymers (Up to 572°F)
PTFE (Teflon): Temperature resistant up to 500°F with excellent chemical resistance and low friction properties.
PEEK: Continuous use temperature of 480°F (250°C) with excellent mechanical properties and chemical resistance.
PPS (Polyphenylene Sulfide): A robust semi-crystalline thermoplastic with continuous use temperature of 428°F. Low water absorption provides good dimensional stability and excellent electrical properties.
PI (Vespel) and PAI (Torlon): High-performance polymers capable of temperatures approaching 572°F, though significantly below metal capabilities.
Low-Temperature and Cryogenic Fastener Materials
Austenitic Stainless Steels (Down to -450°F)
300 Series (304, 316, 310): These steels maintain or increase strength, ductility, and toughness at low and cryogenic temperatures down to near absolute zero. The face-centered cubic (FCC) atomic structure resulting from nickel addition prevents the brittleness that plagues body-centered cubic (BCC) metals at low temperatures.
310 Stainless: Offers low-temperature usability down to -450°F while retaining toughness and low magnetic permeability. A fully stable stainless steel that cannot transform at cryogenic temperatures.
Caution: Some austenitic grades like 301, 302, 304, and 321 can partially transform to BCC structure under combination of gross plastic deformation and cryogenic temperatures, resulting in impairment of ductility and toughness.
Aluminum Alloys (Excellent Cryogenic Performance)
Aluminum and its alloys perform exceptionally well in cold environments. Tensile strength and yield strength often increase while retaining excellent ductility, making them popular for cryogenic applications. Used extensively in cryogenic tanks and aerospace structures.
Nickel-Based Alloys (Wide Temperature Range)
Inconel 718: Proven usability from -320°F to 1300°F, offering a remarkable temperature span. Extremely strong with maximum UTS up to 210 ksi and excellent corrosion resistance.
Inconel 625: Ideal for cryogenics with excellent ductility and strength at low temperatures.
Monel 400 and K-500: Usable from -320°F up to 1000°F. Monel 400 demonstrated good toughness and ductility down to -320°F in testing. K-500 offers increased strength with little loss to ductility and toughness down to the temperature of liquid hydrogen. Both offer unmatched protection to hydrofluoric acid and excellent saltwater resistance.
Titanium Alloys (Lightweight Cryogenic Option)
Ti-5Al-2.5Sn ELI: Extra low interstitial material maintains excellent ductility and toughness at ultra-low temperatures, suitable for liquid hydrogen and oxygen applications.
Ti-6Al-4V ELI: High specific strength-to-weight ratio with good low-temperature ductility in specific grades, vital for aerospace applications requiring low heat leakage.
Note: Titanium requires careful attention to crack tolerance at cryogenic temperatures. Some alloys can absorb hydrogen when exposed to high temperatures in gaseous hydrogen atmospheres, forming hydride platelets that reduce subsequent low-temperature notch/tensile strength.
Copper Alloys (Good Cryogenic Properties)
Brass: Usable at cryogenic temperatures while maintaining good ductility. Free-machining brass (65% Cu, 32% Zn, 3% Pb) provides economical option for low-temperature applications.
Phosphor Bronze and Beryllium Copper: Maintain properties at cryogenic temperatures with good strength and ductility.
High-Temperature Polymers for Cryogenic Use
PTFE: While losing flexibility at low temperatures, PTFE retains lubricity, abrasion resistance, and strength down to -328°F (-200°C). Shows little or no brittleness even at this frigid temperature and remains highly flexible to nearly -100°F.
Material Selection Decision Matrix
For High-Temperature Applications
Below 800°F: Standard austenitic stainless steels (304, 316) provide adequate performance for most applications at reasonable cost.
800-1300°F: Specify high-temperature stainless grades (309, 310, 630) or A-286 for combined strength and oxidation resistance. Consider thermal cycling requirements.
1300-2000°F: Nickel-based superalloys (Inconel 600, 601, 625, 718, Waspaloy, Alloy 330) become necessary. Select specific alloy based on strength requirements, corrosive environment, and cost constraints.
2000-3600°F: Refractory metals (molybdenum, tantalum) required but only in oxygen-free environments. Evaluate whether vacuum or inert atmosphere can be maintained.
Above 3600°F: Ceramic fasteners (alumina, zirconia) are the only option. Accept trade-off of limited mechanical strength and brittleness. Avoid applications with vibration or shock loading.
For Low-Temperature and Cryogenic Applications
Down to -100°F: Most austenitic stainless steels and aluminum alloys perform well. Standard 300-series stainless steels are economical choices.
-100°F to -320°F: Specify austenitic stainless steels (304, 316, 310), aluminum alloys, nickel alloys (Inconel 718, 625, Monel 400, K-500), or certain titanium alloys. Avoid carbon steels and ferritic/martensitic stainless steels due to DBTT concerns.
-320°F to -450°F: Use 310 stainless steel, Monel alloys, Inconel 718, or specialized titanium alloys (Ti-5Al-2.5Sn ELI). Aluminum alloys continue to perform well.
Below -450°F (near absolute zero): Limited to austenitic stainless steels like 310 or specialized cryogenic alloys developed for superconducting magnet applications.
For Wide Temperature Range Applications
-320°F to 1300°F: Inconel 718, Monel K-500, A-286, or 310 stainless steel provide performance across this extreme range. Select based on specific temperature dwell times, cycling frequency, and environmental factors.
Industry-Specific Applications
Aerospace: Titanium alloys for cryogenic fuel tanks, Inconel for turbine components, A-286 for high-temperature structural fasteners, ceramics for thermal protection systems.
Automotive: Austenitic stainless steels for exhaust systems, A-286 for turbocharger applications, high-temperature polymers for underhood components away from direct heat exposure.
Oil and Gas: Monel for subsea equipment experiencing temperature swings, Inconel for downhole tools in high-temperature wells, austenitic stainless for LNG storage and transport.
Power Generation: Alloy 330 for boiler applications, Inconel for gas turbine hot sections, austenitic stainless for steam systems.
Semiconductor Manufacturing: Tantalum for high-temperature vacuum processing, ceramics for plasma chambers, specialty alloys for chemical resistance combined with temperature extremes.
Cryogenics: Aluminum alloys for lightweight tanks, austenitic stainless steels for valves and fittings, PTFE for seals and gaskets.
Testing and Validation
Before committing to production, validate material selection through:
Thermal Cycling Tests: Expose fasteners to representative temperature cycles including ramp rates, dwell times, and number of cycles expected in service.
Mechanical Property Testing: Verify tensile strength, yield strength, hardness, and ductility at operating temperatures, not just room temperature values.
Corrosion Testing: Evaluate oxidation resistance at elevated temperatures or environmental stress cracking at low temperatures in service environment.
Joint Simulation: Test complete assemblies under thermal and mechanical loading to verify that fastener performance translates to actual joint performance.
Procurement Considerations
Material Certification: Request material test reports (MTRs) documenting chemistry and mechanical properties, especially for aerospace and critical applications.
Heat Treatment Verification: Confirm that fasteners received the specified heat treatment. High-temperature alloys often require precise heat treatment for optimal properties.
Coating Compatibility: Verify that any coatings or platings are compatible with operating temperatures. Many standard coatings degrade or outgas at elevated temperatures.
Lead Times: Specialty alloys and custom configurations may have extended lead times. Plan procurement accordingly for project schedules.
Cost Management: Balance performance requirements with budget constraints. Specify the minimum performance level needed rather than defaulting to premium alloys when standard materials suffice.
Conclusion
Selecting fastener materials for extreme temperature applications requires understanding how temperature affects material properties, identifying relevant failure modes, and matching materials to specific operating conditions. The range of available materials is broad, from economical austenitic stainless steels for moderate temperature swings to exotic ceramics for ultra-high-temperature furnace applications, and from standard aluminum alloys for cryogenic service to specialized superalloys for aerospace turbines.
Key principles for successful selection include:
- Define the actual temperature range, cycling frequency, and duration of exposure
- Understand environmental factors beyond temperature (corrosion, oxidation, chemicals)
- Select materials with proven performance in similar applications
- Validate selection through testing before production commitment
- Balance performance requirements with cost and availability constraints
Whether specifying fasteners for automotive underhood applications, aerospace cryogenic systems, industrial furnaces, or oil and gas downhole tools, proper material selection ensures reliable performance, prevents costly failures, and maximizes the service life of critical assemblies.
Where Does CFI Fit In?
For over 30 years, Components for Industry has been a worldwide provider of industrial components and a trusted partner for companies in industrial plastics and composites, including Automotive at the OEM level. If you want more information about CFI and our industrial components including threaded inserts, brackets, and clips, contact us at 847-918-0333 or sales@componentsforindustry.com.
