Inconel® is a material that is specifically optimized for some of the toughest use conditions to be found in manufacturing. Even compared to stainless steel, Inconel® has an incredibly high tolerance for extreme heat, and doesn’t lose as much tensile strength at 2,000°F as most varieties of steel.
However, Inconel® is an expensive material, one which is best reserved for the right use conditions where other materials won’t work as well. With this in mind, here is an explanation of Inconel’s® properties, as well as a few examples of uses where Inconel® would be preferred over most formulations of stainless steel:
How Strong is Inconel®?
When determining strength, tensile strength, corrosion resistance, and even melt resistance can be measured. Inconel 625® has a high tensile strength range of 103 - 160 ksi compared to the 73.2 ksi of stainless steel and can maintain that strength at higher operating temperatures.
Though exact measurements vary, reported statistics state the range of the Inconel melting point between 2,350°F and 2,460°F (1,290°C and 1,350°C). While the Inconel melting point is lower than that of stainless steel, Inconel 625® is stronger than stainless steel at high temperatures while being more resistant to oxidation and scaling as well.
Inconel® is considered a superalloy due to being well suited for extreme pressure and heat environments as well as being corrosion resistant. However, stainless steel alloys are often more suitable for sterile manufacturing or medical applications. A superalloy like Inconel® tends to be better for heat treating applications and other high-temperature processes.
What is Inconel 625® Used For?
In the high-nickel superalloy Inconel® family, Inconel 625® is between Inconel 330® and 600 when it comes to nickel content. This combination, along with columbium and molybdenum, allows for this type of Inconel® melting point to be very high and perform well in high heat. Inconel 625® is especially resistant to chloride pitting, fatigue stress, and has a particularly high creep rupture strength and high oxalic resistance. Additionally, Inconel 625 is very easy to weld when compared to other Inconel® variations.
Due to its high chemical and temperature resistant qualities, the superalloy Inconel 625® can be used in a variety of applications, including jet engine exhausts, flare stacks, seawater equipment, and chemical plant equipment.
What is the Difference between Monel and Inconel®?
Monel® is another metal consisting of a nickel-copper alloy. Like Inconel®, which is a nickel-chromium alloy, Monel® can be used in extreme conditions with high heat.
Monel® metal consists of a group of nickel alloys that have a strong corrosion resistance to chemicals, heat, and other agents including seawater. Created at the turn of the 20th century, Monel® has been used in applications ranging from aerospace applications during the Space Race to the World War dog tags. The nickel alloy is still used extensively today but is more expensive than most other alloys.
Since Inconel® is a nickel and chromium alloy, it’s resistant to oxidation and is ideal for jobs with different gasses and large temperature discrepancies. Applications in the oil and gas extraction, aerospace, and medical industries would be better suited for Inconel®. In comparison, Monel’s® copper additive provides it enhanced corrosion resistance and makes it particularly strong against sea water as well as hydrochloric and sulfuric acids.
Additionally, Monel® 's strengths make it ideal for saltwater as applications as well as chemical processing applications. When compared to the Inconel melting point, Monel® ‘s melting point range is very similar at 2370-2460° F.
Five Inconel® Use Case Examples
Oil & Gas Extraction
Inconel® is ideally used in the oil and gas extraction industries due to its high temperature resistance and oxidation resistant properties. The oil and gas industries need a superalloy metal, like Inconel®, that can withstand extreme environments and volatile, corrosive gasses.
The superalloy Inconel 625® is especially useful for the processing systems required for natural gas production. Due to Inconel 625’s® particularly strong thermal fatigue strength and oxidation resistance, it’s often used for the separation of extracted fluids or in line steel transfer piping.
Heat Treat Applications
Inconel® is famously resistant to extreme temperatures, and retains enough tensile strength at high temperatures to continue holding moderate loads (Inconel 625® retains 13.3 ksi tensile strength at 2,000°F). This makes Inconel® the ideal basket material for heat treat applications—comparing favorably to stainless steel alloys such as Grade 304, 316, and 330 SS.
Compared to most stainless steel alloys, a basket made from a superalloy like Inconel® won’t lose shape as easily when holding parts through a rigorous heat treat application.
Rapid Temperature Changes
Some manufacturing processes may combine high and low temperature processes in rapid succession. Most Inconel® alloys retain excellent oxidation resistance at high and low temperatures, allowing a single basket made from Inconel® to be used in processes where temperatures vary between near-cryogenic lows and heat treatment highs.
Inconel® is often used in marine applications because of its extraordinary resistance to sodium chloride (salt) at a variety of temperatures. So, for processes that use salt or factory locations near the ocean, Inconel® can be ideal for a parts washing basket.
However, some stainless steel alloys also exhibit excellent resistance to saltwater. So, when would Inconel® be considered preferable?
Generally speaking, this superalloy would only be much more useful than grade 316 stainless steel if extreme temperatures in excess of 1,000°F would be a concern as well. Inconel® would retain its oxidation resistance better at high temperatures than 316 SS would.
Some of Marlin’s manufacturing clients might use Inconel® in the construction of jet engines and turbines.
Jet engines are unique in that they have to withstand extreme temperatures both high and low frequently during use. As noted on the meteorology training website, at 36,000 ft. (well within a passenger jet’s standard cruising altitude), the average air temperature is -56.3°C (-69.3°F), but the combustion process can exceed temperatures of 1,150°C (2120°F).
Cooling technologies are used to rapidly reduce temperatures, but they can still easily exceed the tolerances of many metals. Inconel 600® retains high oxidation resistance and tensile strength despite rapid changes in temperature from the combustion process and cooling technologies employed in the aerospace industry.
Basically, Inconel® is an ideal material whenever extreme temperature and chemical resistance are a must, and for any process where temperature highs would normally degrade the oxidation resistance of other metals.
However, Inconel® isn’t the only answer to different parts handling basket engineering challenges. To get the best basket for the job, it’s important to consider every aspect of your manufacturing process and needs compared to the capabilities of numerous types of metal.