How high temperature affects fasteners (HY-industry technical centre)
High temperature environment is very common in fastener applications. It places additional requirements on the selection of fasteners. At this time, you need to pay special attention to the type of fasteners, because high temperature will affect the service life of the fasteners and the fatigue of the joints. Strength has an important effect.
How does high temperature affect fasteners
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When most conventional fasteners are exposed to high temperatures, one of the biggest challenges they face is oxidation. Most people would think that the main problem at this time is the melting of fasteners, but when the temperature is 1000 degrees Fahrenheit (537 degrees C) or lower, most metals will not, except for softer metals. Melted. -
Another problem that may be encountered is the rapid expansion of fasteners at high temperatures. This will result in an increase in the installation hole diameter, and when cooled, as the fastener shrinks in the radial direction, the bond between the fastener and the hole will become loose. This kind of “clearance fit” hole is very prone to failure under high vibration conditions.
Different alloys you can trust at high temperatures
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In order to use fasteners to connect in high temperature environments, you can usually only choose alloy materials, because you can combine the advantages of multiple metals, which can make the fasteners more resistant to high temperature and oxidation. Common high-temperature application alloys include :
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Incoloy A286: This is an alloy of iron, nickel and chromium. It has excellent mechanical properties, and is very resistant to oxidation and high temperatures. Its only disadvantage is that the above advantages can only be applied below 1200 degrees Fahrenheit (650 degrees Celsius). Above this critical temperature, the metal is likely to have begun to oxidize, and when exposed to higher temperatures, it will eventually melt. -
Nickel-based alloys: Nickel is a versatile element that can easily form alloys with many other metals, such as chromium, iron, molybdenum, and copper. Therefore, there are many nickel alloys in practical applications. These alloys all exhibit excellent corrosion resistance and High temperature corrosion performance. But it should be noted that the application critical temperature of nickel-based alloys is about 1600 degrees Fahrenheit (870 degrees Celsius).
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Sometimes, we may face higher application temperatures. At this time, we may need to consider the use of high alloy content of molybdenum, tungsten and other alloys. Some tungsten alloys can still maintain their mechanical properties even when the temperature exceeds 3000 degrees Fahrenheit (1650 degrees C). The role of performance.
Other issues that need attention
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In the case of rapid changes in application temperature, in addition to the loss of the strength of the fastener itself, the most important thing is probably the surface plating or coating. For example, an ordinary cadmium-plated bolt will begin to melt when the temperature exceeds 450 degrees Fahrenheit (230 degrees Celsius). For higher temperature environments, the surface treatment needs to appropriately increase the nickel content to effectively deal with the corrosion at high temperatures, and at the same time pay attention to reducing the wear and abrasion of the thread. In the range above 900 degrees Fahrenheit to 1400 degrees Fahrenheit (480-760°C), silver plating is the best choice.
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Finally, it is necessary to mention a ceramic material. Although higher heat resistance can be obtained, such as alumina ceramics, its disadvantage is that it is not strong enough and easy to crack. Therefore, this type of material is very suitable for use in environments that are unlikely to be impacted.
