High temperature environments are one of the harshest for parts, and using the right materials is essential for functionality. When temperatures rise, most materials expand and become weaker. When there are moving parts, this can become a big issue.
There are some metals and alloys that perform better in high temperatures.
Some of the best high heat resistant metal alloys include titanium, stainless steel, nickel alloys, and certain steel alloys. Here’s an overview of some of the best metals for high-temperature environments and why they work well.
The most important factor when choosing a heat-resistant alloy is the melting point of the metal. When a metal gets closer to its melting point, it becomes more flexible and loses its tensile strength. This can cause parts to bend, dent, or break.
Metals with the highest melting point include: Tungsten (6188°F), Rhenium (5756°F), Molybdenum (4748°F), Chromium (3464°F), and Titanium (3034°F).
The second important factor is the expansion rate. Nearly every material expands as it gets hotter. Different metal alloys expand at different rates when they’re heated up. The more a part expands and contracts during temperature changes, the faster the structure of the part will weaken. When the parts heat up and cool down, they can develop cracks and weaken over time. Ideally, you want to choose a metal with lower expansion rates so the parts continue to function properly.
Titanium is the go-to choice for high-temperature applications. Titanium has one of the highest melting points, and one of the best strength to weight ratios. It’s commonly used for luxury car parts and aerospace components. Titanium alloys also handle extreme temperature changes better than most other metals.
The biggest downside to titanium is the costs. It’s more expensive as a raw material, and more expensive to machine because of the specialized cutting tools required.
Stainless steel alloys are also highly durable and can handle high temperature environments. Chromium is the primary element that makes stainless steel stainless. And because Chromium has a very high melting point, it makes stainless steel alloys great for high temperature applications.
There are many different alloys of stainless steel, and some have better temperature resistance. The best stainless steel grades for high heat are 304, 309, 310, and 316. 310 stainless steel can handle working temperatures ~2,000° F. These alloys contain Nickel and Molybdenum which increases the melting point. 400-series alloys can be stronger, but they have a significantly lower temperature limit.
Nickel alloys are also called superalloys. These metals are extremely durable, but also more expensive, so they’re reserved for high-stress working environments.
Hastelloy X is a Nickel alloy with excellent high temperature strength and oxidation resistance. This is most commonly used in gas turbine engines because of its high heat tolerance.
Inconel is another Nickel-based superalloy that’s highly resistant to temperature. Its chemical makeup is very similar to Hastelloy. Inconel alloys have small amounts (0.5-1%) of Copper and Aluminum that Hastelloy doesn’t have. This helps form a thick oxide layer that protects the surface from damage when the material is heated.
Steel isn’t the best option for high-temperature applications, but some steel alloys are suitable. Steel is also the lowest cost and most widely available material, so it can be a great option for parts that require moderately high temperature resistance.
The best steel alloys for high temperature application are 4000-series alloys, and M-grade steel alloys. 4000-grade alloys have small amounts of Chromium and Molybdenum, which increases strength. M-grade steel alloys (M2, M35, and M42) are often used for broaches and cutting tools. These alloys have higher strength and maintain their strength better when hot.
Most steel alloys can also be heat treated, which increases the hardness and durability of the parts.
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