When starting a new manufacturing project, one of the first decisions you have to make is what metal to use. This can be a difficult choice, as there are many factors to consider.
The type of metal used will affect the strength, weight, and cost of the final product.
Two of the most popular types of metals used for manufacturing nowadays are Inconel and stainless steel.
While both of those materials are strong and durable, there are some key differences between the two.
The choice will almost entirely depend on which specific properties you need for your project.
In this guide, we will explore some of the basic characteristics and features of Inconel and stainless steel.
We will also look at what sets them apart and which applications each of them is most suitable for.
Inconel is a group of austenitic superalloys made primarily out of nickel and chromium, in addition to some other materials in smaller percentages.
It is known for its ability to resist oxidation, high temperatures, corrosion, and creep.
Since Inconel alloys can handle a tremendous amount of heat and pressure without deforming or cracking, they are used in a variety of industries where pressure and heat are commonplace.
Inconel alloys were first developed in the first half of the 20th century. The first alloy of its kind, Inconel 600, was created to resist corrosion from acids and other chemicals.
Because it also boasted a high-temperature resistance, it was initially used in aircraft engines.
After the 1940s, other grades of Inconel that were stronger and more resistant to corrosion were developed to meet the demands of industries whose machinery and manufactured products operated in harsh environments.
To this day, Inconel alloys continue to find many applications across a variety of industries.
Since there are so many different grades and forms of Inconel, the compositions can vary widely.
However, as mentioned earlier, each grade will always have some amount of its foundational elements —nickel and chromium.
Here are the materials that Inconel is typically made up of, along with their percentages:
Other elements such as molybdenum, aluminum, and titanium may be added as well.
As mentioned earlier, Inconel alloys are primarily known for their high strength and resistance to corrosion and temperature extremes.
When Inconel is heated, a passivating, thick oxide layer forms on its surface. The layer is stable and, as such, it protects the surface from further changes.
Inconel alloys retain their strength in a wide range of temperatures.
Where other alloys would deform due to thermally induced crystal vacancies, Inconel alloys hold up. This makes them an attractive choice for applications in high-temperature environments.
Inconel alloys also exhibit low thermal expansion and good electrical and thermal conductivity, making them well-suited for electronic and electrical applications.
While all Inconel alloys share certain characteristics, they also exhibit a unique set of properties that determine each one’s suitability for certain applications.
The most common uses for these superalloys include:
As you can see, no matter their use, Inconel alloys are almost always subjected to extreme conditions.
Stainless steel is an alloy that consists of iron, chromium, and other metals.
It has excellent resistance to staining, rusting, and corrosion, which is why it has a variety of applications across numerous industries.
The history of stainless steel begins with a British metallurgist named Harry Brearley.
In 1913, while working in Sheffield, England, Brearley was investigating the addition of chromium to molten steel in order to improve its corrosion resistance.
He found that when he added chromium to certain steels, they not only resisted rusting but also did not discolor when heated—unlike the kinds of steel known at the time, which became dull red when heated.
Ever since its discovery back in the early 1900s, the popularity of stainless steel has continued to grow, as its attractive surface and durable nature complements many manufactured metal components.
Stainless steel’s primary composition includes iron and at least 10.5% chromium.
This level of chromium creates a thin layer of oxide on the surface, which prevents the corrosion of the material.
There are over 150 grades of stainless steel, each with unique physical and chemical properties.
All these grades have been categorized into five major classes:
Their composition can be found in a table further along in this post. Each has distinct properties that are useful for different applications, environments, and settings.
Stainless steel has a host of properties that offer many benefits to businesses looking for custom-manufactured metal parts.
Durability, corrosion resistance, and low maintenance are just some of the properties that have made stainless steel one of the most widely used metals in the world.
As was discussed earlier, there are five primary classes of stainless steel.
The most common properties shared by all five of those classes include corrosion resistance, strength, and durability.
The only difference is the degree (higher or lower) to which each one manifests them.
You can find all of them listed in the table below, but before that, let’s go over their uses.
The ubiquity of steel in manufacturing and architecture is a result of the many advantageous properties just discussed.
Another advantage of stainless steel is its low carbon footprint which helps to mitigate the effects of air pollution.
Stainless steel is a versatile material that can be utilized in a variety of applications and industries, which is one of the main reasons its usage has increased exponentially in recent years.
This growth is expected to continue as more industries adopt this material for their manufacturing projects.
Here’s an overview of the five classes of stainless steel, their composition, properties, and uses.
| Class | Composition | Properties | Uses |
|---|---|---|---|
| Austenitic | 16-30% chromium 20% nickel | non-magnetic, high ductility, toughness, resistance to stress corrosion cracking | kitchen utensils, medical instruments, architecture, chemical processing equipment |
| Ferritic | 10-27% chromium little to no nickel | good corrosion resistance, high-temperature resistance, ductility, machinability | car exhaust systems, heat exchangers, boiler tubes, surgical instruments, magnetic shielding |
| Martensitic | 12-18% chromium 0.1-1.50% carbon | high strength, hardness, versatility, heat-treatability | knives, surgical instruments, other cutting tools |
| Duplex | 19.5-30% chromium 3-6.5% nickel ~5% molybdenum | high strength, high corrosion resistance, excellent weldability, good mechanical properties, resistance to stress corrosion cracking | pressure vessels, storage tanks, pipelines, desalination plants |
| Precipitation Hardening | 14-17% chromium 4-25% nickel | hardness, toughness, durability, high strength, wear resistance, heat-treatability | pump shafts, valves, fasteners |
Keep in mind that, like with Inconel, each of the classes can also contain other metals, but in much smaller percentages.
Now that we’ve covered these classes, let’s compare the features of stainless steel with those of Inconel.
There are several key differences between Inconel and stainless steel.
The first one lies in their primary composition.
Inconel is an alloy of nickel, chromium, and molybdenum, while stainless steel is an alloy of iron, chromium, and carbon.
This difference in composition directly affects the three most important factors in deciding which one is more suitable for a specific manufacturing project: cost, temperature, and strength.
Let’s take a look at each of them.
Inconel is more expensive than stainless steel. This is largely because Inconel is more difficult to produce, due to its high melting point and resistance to oxidation.
Moreover, the process of manufacturing Inconel is also time-consuming, as the alloy must be cooled slowly to prevent brittleness.
So, keep this in mind if your project requires tight control of the expenses.
Inconel alloys are well-suited for high-temperature applications.
Inconel has a very high melting point—between 2,350°F and 2,460°F (1,290°C and 1,350°C).
Like Inconel, stainless steel can also be used for high-temperature applications.
The melting point of stainless steel is between 2550°F and 2790°F (1400°C and 1530°C).
However, while Inconel and stainless steel can both be used in high-temperature applications, Inconel is better suited for high-temperature environments due to its increased resistance to oxidation and corrosion at higher temperatures.
Inconel is able to maintain its strength and integrity at high temperatures, even at temperatures that exceed 2000° F. This makes it one of the most durable metals on the market.
On the other hand, stainless steel is stronger than Inconel at lower temperatures.
This is particularly true of austenitic stainless steels, which are able to maintain their structural integrity and strength even in sub-zero temperatures.
The choice between Inconel or stainless steel will depend on what environment the material is going to be exposed to, the required strength of the material, and the price requirements for the specific project.
Inconel is best used in harsh environments that require the material to be resistant to thermal shock, corrosion, and oxidation at high temperatures.
Inconel alloys are the best choice for high-temperature applications where oxidation and carburization are common.
Moreover, since Inconel alloys are also resistant to chloride-ion stress-corrosion cracking, they are good candidates for use in saltwater applications.
However, Inconel alloys are not suitable for use in environments that are highly acidic or alkaline, or in environments where there is a risk of hydrofluoric acid attack.
They are also not the ideal choice for applications where high levels of radiation are present.
Since stainless steel has the dual ability to resist rust and corrosion, it is an ideal choice for applications where hygiene is important, e.g., in hospitals or food processing plants.
Stainless steel is also commonly used in architecture and construction because it is more corrosion-resistant than traditional steel, and therefore is able to maintain its aesthetic appeal for a longer period of time.
All in all, stainless steel is a better option than Inconel when a less expensive, more abundant, and easy-to-work-with material is required.
It is also the better option when the material will be subject to low to medium-high temperatures—up to 900°F (482°C)—as it maintains its strength and resistance levels better at these lower temperatures.
However, as with Inconel, there are a couple of instances when stainless steel is not the best material for the job.
Firstly, most grades of stainless steel are magnetic, so if a material that’s non-magnetic is required, then stainless steel probably isn’t going to be the right choice.
While austenitic grades of stainless steel are non-magnetic, ferritic and martensitic grades are attracted to magnets.
Secondly, if an application requires a material with a high melting point, then Inconel is a better choice as it maintains its strength and corrosion resistance much better at higher temperatures.
When choosing a metal for a particular application, it is important to consider the properties that are most likely to affect it.
In the case of Inconel and stainless steel, both are popular metal alloys with distinct properties that make each one more or less suited for different applications operating within a variety of industries.
Inconel’s high strength and corrosion resistance in high-temperature and high-pressure environments make it more suitable for uses within aerospace, chemical processing, and pollution control industries.
On the other hand, the high strength, durability, low maintenance, and aesthetic appeal of stainless steel make it ideal for a broad range of applications within the food and beverage and medical industries, construction and architecture, as well as for the production of household appliances.
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