Welding is the process of using extremely high temperatures to melt separate pieces of metal or metal alloys together for industrial purposes. Usually, alloys tend to be more difficult to weld since they have higher melting points than pure metals.
Inconel is a family of metal alloys that have a high percentage of nickel-chromium composition, known not just for their extreme heat tolerance but also their tensile strength.
So how do you weld Inconel? While welding Inconel is tough, it is not impossible. However, you need to weld them the right way, or they may end up cracking and ruining the workpieces.
Characteristics of Inconel
Inconel is often considered a superalloy since it has features that make it desirable for many purposes. Since Inconel alloys are corrosion-resistant, they are suitable for extreme environments with varying pressure. They also do not react easily with oxygen in the air, which means they are able to withstand very high temperatures as well. When the alloys are exposed to heat, they form a protective layer across the surface that keeps the metal safe from damage.
Besides heat resistance, Inconel alloys are also extremely strong, even when heated. This strength is due to the solid solution strengthening or precipitation strengthening traits, though it depends on the alloy’s composition. Their resistance to pressure makes them useful for many different kinds of extreme applications.
Uses of Inconel
Most applications of Inconel occur in a very extreme environment since the alloy is expensive and can often be replaced with stainless steel in circumstances where the environment isn’t as severe. Here are some of the more common uses of Inconel:
Aerospace & Jet Engines
Nickel alloys are commonly used in the aerospace industry. Since engine parts are exposed to such high temperatures and pressure, the material needs to be able to withstand such environments and not lose their strength. Inconel is used in jet engines and components of the airframe, such as turbine seals and exhaust liners. Inconel has high mechanical strength and offers creep resistance under very high-stress conditions, making it a useful component for aerospace applications.
Extraction of Natural Resources
Inconel alloys are commonly used in the extraction of oil and gas. Design engineers need to keep many factors in mind here when it comes to selecting materials since the temperature can rise up to very high levels, and the raw substance that is being extracted and processed is very volatile and corrosive.
Here, Inconel is used to separate the extracted fluids within the processing system to produce liquefied natural gas. Inconel offers excellent fatigue strength and resistance to oxidation as well as high tensile strength, making it an excellent choice for such processes.
Car engines generate a lot of heat, but they need to be lightweight and reliable at the same time. Engineers need to consistently find materials that can keep up with the advancements in technology, while also providing the features that people look for in cars such as more power, higher thrust, and environmental friendliness.
Inconel proves to be useful here as well since it is so versatile and resistant. Inconel alloys are frequently used in ignition systems, safety devices, sensors, and electrical switch gears.
Because of the high heat and pressure resistance, Inconel may seem like it is difficult to weld, but once you understand the issues you may face, it is doable.
Nickel as an alloy is known for high heat tolerance, but when welded, they have a tendency to crack, which can be a problem. However, there are alloys that are designed to be welded. The weld pool and fillers often look poorly defined and unattractive during the welding process. However, when it is carried out correctly, they are resistant to corrosion and hold up as you would expect and want them to.
Using Inconel 625 as a Filler Metal
Inconel 625, which contains a high composition of Niobium, is often used as a filler metal to join two pieces of Inconel alloys together, and usually also when the two parts being welded are not of similar compositions. Why use Inconel 625 and not another metal that is easier to melt? Using a metal that is significantly different from these metals can cause problems, such as thermal expansion and bimetallic corrosion, when they are exposed to such high temperatures.
Using TIG Welding for Inconel
TIG welding is recommended for welding Inconel since it provides a more significant amount of control when using a skilled welder compared to when using GMAW and SMAW methods. TIG welding doesn’t usually use filler metals. However, adding one is more practical for welding Inconel than depending on the high melting points of the alloys since it becomes hard to fuse them without cracking them.
Using Automated Machines
Manually welding can be inconsistent since the first few welds are often sloppy as you start understanding how to go about it, and the last few suffer as well due to fatigue. This, along with the fact that welding machines are heavy and hot, makes the process potentially dangerous.
Using automated welding machinery for welding Inconel is the right choice.
Programming a robot to do dangerous, heavy work while under supervision is a safer alternative to having a person holding a welding rod and arc welder for the Inconel. It protects against the welding filler that could drip and cause burns and sparks.
Automated machinery is consistent from the get-go since they don’t have to get into the zone or get tired due to repetitive motions. The welding process can continue for hours under supervision.
Some welding machines are able to improve quality by making sure that welding is done with precision. This speed is kept in check to avoid any burns and distortions and keep the welded parts of Inconel within their tolerance levels.
Inconel vs. Monel
Often, Inconel can be replaced with Monel as an alloy. Inconel is a nickel-chromium alloy while Monel is a nickel-copper alloy, and it also has very high corrosion resistance. It also has the advantage of having good weldability and is also extremely strong.
Monel is often welded through different processes such as TIG welding, MIG welding, and submerged arc welding. Monel filler metals are used for this since they have the same high strength and resistance to corrosion that Monel alloys do. Different compositions of Monel alloys have different characteristics that make them useful for a large variety of things across industries.
Monel can also be brazed, soldered, and used in different shapes and forms, including wires, flat sheets, and even tubing.
Surprisingly, despite Monel’s strength against extreme temperatures and corrosion, it is not just used in applications like marine or chemical equipment like you would expect. It is also used for regular purposes, such as military dog tags and roofing in large cities.
However, Monel is better known for its corrosion resistance and not as much for the ability to withstand extreme conditions such as temperature or pressure; hence, the use of Inconel versus Monel depends on these factors as well.
Is Inconel toxic?
Under usual circumstances, handling Inconel alloys is not very much of a health hazard for anyone. However, in cases of fabrications, such as grinding, melting, and welding, the processes may produce dust and vapor as fumes. If these are inhaled, they may cause metal fume fever, which could present itself in the form of symptoms that are similar to those of the flu, such as fever, fatigue, or chills. The dust produced in fabrication may irritate the lungs, eyes, or skin.
What are the properties of Inconel?
Inconel is most commonly known for its property of being extremely strong. Inconel alloys are resistant to very high temperatures because heating causes a stable oxide layer to form over the surface. Inconel is also very resistant to pressure, oxidation, and corrosion. Inconel alloys are called superalloys because of the mechanical properties that allow them to be used in chemical and aerospace industries.
What are the most common applications of Inconel?
Inconel is used mostly for applications that require heavy resistance, such as for propeller blades and submarine fittings, motors, etc. Inconel is also frequently used where sea-water exposure is frequent since it will provide resistance against corrosion. It is also used for aerospace in exhaust systems, hydraulic line tubing, and heat-exchange tubing as well. It is also used in pollution control systems to get rid of polluting items that could corrode other materials.