How to choose fasteners for high-temperature applications
A guide to high-temperature fasteners
To help you make the right choice for fasteners that can withstand high temperatures, we’ve put this guide together to cover:
The effect of heat on metal fasteners
Industries ranging from automotive to HVAC rely on fasteners that perform in high-temperature environments. Metals do have temperature limits. Melting is typically not a problem for metal unless we’re talking about temperatures of 538˚C or higher.
Without heat-resistant metals, your fasteners will suffer. High temperatures affect fasteners in various ways:
1. Corrosion
There are different types of high-temperature corrosions, but they typically involve a chemical attack from gases, molten metals or salts.
2. Weakened material strength
Metal weakens and becomes more ductile at high temperatures, while extremely low temperatures cause it to become brittle.
3. Expansion and contraction
High temperatures can also make metal fasteners expand, putting pressure on the holes they’ve been installed into. When the metal cools, the fastener will contract and loosen.
Considerations before choosing your fasteners
High-heat bolts, high-temp washers, heat-resistant rivets and other fasteners have specific mechanical properties. In order to select a fastener, you need to consider materials. Before you can do that, you have to determine:
- The average temperature your fastener will be exposed to
- The length of time the fastener will endure extreme temperatures
- If the fastener will experience vibration or shock
- If corrosion poses a threat to the fastener
- If you want your fastener to conduct electricity or not
Additives can give you more heat resistance, whether your fasteners will be metal or plastic. You’ll find that a material varies in maximum service temperature, per manufacturer. This is due to the additives the manufacturer uses. For example, one manufacturer might formulate a material to operate at around 301˚C, while another manufacturer offers that same material at 176˚C.
Let’s look at your material choices.
High-strength non-metallic fasteners
Plastics and ceramics fall under this category, although high-temperature ceramic fasteners typically contain tantalum. This is a remarkable compound for its hardness, resistance to chemical attacks and oxidation, and high melting point.
Ceramics
What material can withstand the most heat? Ceramics. An example of a ceramic fastener is the spacer shown here. Spacers separate two components, such as PCBs. The maximum operating temperature for this spacer is 1,700˚C. Ceramics can become brittle at extremely low temperatures, although this spacer can tolerate temperatures as low as -40˚C
Ceramic bolts are another example of a fastener made of this material. Ceramics provide electrical insulation, so if you’re looking for high-temperature, non-conductive bolts, this can be an option.
Keep in mind there are different ceramics, depending on the additive. Ceramics can also be made to incredibly high strength, with co-efficient of thermal expansion similar to that of stainless-steel.
Vibration damping: ✔
Thermal conductivity: X
Electrical conductivity: X
PEEK®
PEEK is a robust, high-performance polymer used in demanding applications. This material tolerates both mechanical and physical stress – yet it’s lightweight – which is why the automotive, electrical and medical industries use it so often.
Among plastics, it has a high-heat tolerance. The socket head cap screw shown here has a continuous temperature use of 176˚C. If your application will involve higher temperatures, appropriate PEEK fasteners are on the market.
Vibration damping: ✔
Thermal conductivity: X
Electrical conductivity: X
Polyphenylene sulfide (PPS)
PPS is a robust, semi-crystalline thermoplastic. Its low water absorption gives it good dimensional stability and excellent electrical properties. It’s often used for electrical components, seals and valves and semi-conductor machinery components.
The shoulder washer shown here can stand up to temperatures of 220˚C. Shoulder washers provide heat and electrical insulation for assemblies, making PPS especially advantageous to use. Also available in black.
Vibration damping: X
Thermal conductivity: X
Electrical conductivity: X
| Maximum temperature | Material | Advantages |
| 180˚C – 300˚C
(350˚F – 572˚F) |
PEEK® |
- Outstanding mechanical and physical properties - Chemical and corrosion resistance - Stiffness, high tensile strength, impact resistance |
| 1700˚C – 2204.2˚C
(3092˚F – 4000˚F) |
Ceramics (Alumina, Zirconia) |
- Extreme temperature & corrosion resistance (Note: becomes brittle at extremely low temperatures) |
| 220˚C – 350˚C
(428˚F – 662˚F) |
PPS |
- Exceptional mechanical strength - Dimensional stability - Good chemical resistance - Resists hot water & steam |
What metal can withstand the most heat?
Is stainless steel heat resistant? What metal can withstand 3000 degrees? Nickel alloys that can withstand extreme heat are below. It’s worth repeating that additives can give you more heat resistance, so this table should not be taken as definitive. Rather, these materials are available on the fastener market at these service temperatures. Use the chart as a guide to getting started with high-heat metals.
Comparing temperatures
| Maximum temperature | Material | Advantages |
| 593.3˚C
(1100˚F) |
Stainless steel 630 |
- Exceptional hardness - Excellent strength - Good ductility |
| 621.1˚C – 1232.2˚C
(1150˚F – 2250˚F) |
Stainless steel 309, 310 | - High content of chromium and nickel provides exceptional corrosion resistance |
| 704.4˚C
(1300˚F) |
A-268/ Alloy 660 | - Alloy of iron, nickel, and chrome enables high strength and excellent oxidation resistance |
| 704.4˚C – 1093.3˚C
(1300˚F – 2000˚F) |
Nickel-chrome-based superalloys (Inconel® 600, 625 & 718) |
- Good oxidation, corrosion & carburisation resistance -Maintains strength in corrosive environments |
| 871.1˚C
(1600˚F) |
Waspaloy® |
- Extreme temperature & oxidation resistance - High strength |
| 1148.8˚C
(2100˚F) |
Alloy 330 |
- Handles extreme temperature changes - Withstands alternate carburizing and oxidizing atmospheres |
High-temperature resistant stainless steel
Stainless steel melting point, Fahrenheit, depends on its chemical composition. It’s the same with ceramic melting point, Fahrenheit, or any other material. Each individual element within the material has its own melting point. This is another reason why stainless steels can have different melting points.
High-temperature stainless-steel alloys make it an excellent material for fasteners. Grades 309 and 310 are the most heat-resistant stainless steels, followed closely by Alloy 330. To learn more about grades, we recommend you read our guide, Understanding stainless-steel grades.
A benefit of stainless steels is that they also perform well in temperatures between -73°C and -184°C. If your application will experience extreme temperatures, you can avoid the problem of expansion and extraction with stainless-steel fasteners.
Did you know?
A metal’s maximum operating temperature is generally around two-thirds lower than its melting point.
Iron alloy 660 material properties
Iron alloy 660 is a stainless steel that contains iron, nickel, and chromium, also known as A-268. The material is often used to make high heat-resistant bolts, heat-resistant washers and other fasteners. With a relatively high nickel content, it’s also known as a nickel alloy. To belong to the family of Alloy 660, a material’s chemical composition must include:
- Ni 24-27.0%
- Cr 13.50-16.0%
- Ti 1.90-2.35%
- Mn 2.0% max
- Mo 1-1.5%
- Si 1.0% max
- V 0.10-0.50%
- Al 0.35% max
Alloy 660’s strength and exceptional resistance to corrosion and high temperatures makes it especially useful to the oil & gas industry. It’s also commonly used in aircraft and industrial gas turbines.
Alloy 330 provides outstanding resistance to carburising and oxidising atmospheres caused by extremely high temperatures. If your application will alternate between extreme temperatures, this is an excellent choice.
Vibration damping: Alloy 630 is a martensitic stainless steel, which gives it excellent qualities for damping vibration, superior to the austenitic stainless steels mentioned above
Thermal conductivity: Stainless steels have very low conductivity
Electrical conductivity: All metals are good conductors of electricity
Other high temperature steel alloys
Waspaloy® is a nickel-based superalloy. Its high strength and resistance to oxidation are why fasteners made of this material are often used in rotating and non-rotating parts in aerospace gas turbines. Inconel® superalloys are similar. Both are trade names.
Assessing superalloys for factors such as vibration damping aren’t as straightforward as it is for particular plastics. So much depends on their microstructures. Nickel-based alloys strengthened by oxide dispersion appear to have superior damping abilities to precipitation hardened alloys.
If vibration damping is a concern for your fasteners, and you want to use a heat-resistant metal – particularly a superalloy – talk to the manufacturer.
Download free CADs and try before you buy
Free CADs are available for most solutions, which you can download. You can also request free samples to make sure you’ve chosen exactly what you need. If you’re not quite sure which solution will work best for your application, our experts are always happy to advise you.
Whatever your requirements, you can depend on fast despatch. Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.