Mechanical Properties of INCONEL Alloy 600
Like all INCONEL nickel alloys, 600 alloy has excellent corrosion resistance and a host of other chemical properties that make it suitable for the harshest, most demanding environments. But this particular high-temperature alloy is especially known for its mechanical properties. These properties make it a versatile choice for a wide range of applications.
In this article, we'll take a closer look at these properties and how different treatments of 600 alloy affect them.
Combination Strength
The primary components of INCONEL 600 alloy are nickel (72%), chromium (14-17%), and iron (6-10%). This combination is key to its high performance and versatile applications.
The proportion of nickel in 600 alloy is carefully calculated to take advantage of nickel's inherent properties-ductility, toughness, and corrosion resistance-while avoiding stress corrosion cracking. Stress corrosion cracking is a common problem for austenitic nickel-chromium alloys in environments where chlorides are present. Chromium enhances 600 alloy's oxidation resistance, while a small but significant amount of iron gives it additional strength.
This means that even among nickel-based superalloys, INCONEL 600 alloy performs well in high temperature, oxidizing and corrosive environments. Depending on the application and processing, it can be used at temperatures from cryogenic to 1095°C.
Tensile Strength
Tensile strength is a key property for high-stress, high-pressure applications. It refers to the maximum stress value that a material can withstand without breaking when stretched. Tensile strength is expressed in thousands of pounds per square inch (ksi). INCONEL 600 alloy has a nominal tensile strength range of 75 to 220 ksi. However, this depends on many factors, such as the state and shape of the material.
To achieve the maximum tensile strength of 220 ksi, 600 alloy requires high-intensity cold working, which is usually combined with heat treatment.
Yield Strength
Yield strength is another important property. Tensile strength measures the critical point at which a material breaks under stress, while yield strength refers to the critical point at which a material begins to deform permanently and cannot return to its original shape and size.
Alloy 600 is often annealed to reduce hardness and make it easier to form. Annealing is a process where a metal is heated to a specific temperature, held for a period of time, and then cooled again. This process can also improve corrosion resistance. In the annealed state, Alloy 600 has a yield strength of 25-50 ksi. Again, this range depends on the shape and condition of the metal.
However, as with tensile strength, high-intensity cold working can significantly increase yield strength. For example, Alloy 600 wire can have a yield strength of 150-210 ksi after cold drawing and spring tempering.
Fatigue Strength
Tensile strength and yield strength are two factors to consider because they affect the service life of a component and whether a component fails suddenly or gradually. Fatigue strength is another important consideration.
Fatigue strength refers to the maximum stress a component can withstand before damage occurs at the molecular level when subjected to cyclic loading. This damage can lead to cracking and ultimately fracture of the component.
Fatigue is a particular risk in corrosive environments, and it is easy to overestimate the number of cycles required to initiate the fatigue process. When a material goes through only a relatively small number of cycles before it starts to crack and fail, this condition is known as low cycle fatigue. Typically, this is caused by repeated application of the same cyclic stress at values below the material's yield strength. Multiple, rapidly fluctuating stress cycles can lead to high cycle fatigue.
While the yield and tensile strengths of INCONEL 600 alloy are significantly affected by its processing, fatigue is not. Alloy 600 consistently exhibits good fatigue strength in low cycle fatigue tests, regardless of grain size (which is related to heat treatment) and is not affected by changes in other mechanical properties. Only under high cycle fatigue conditions does the fatigue life of the component change.
Impact Strength
Impact strength – the ability to withstand impact without cracking or deforming – is where INCONEL Alloy 600 excels. Measured in foot-pounds, Alloy 600 can deliver 160-180 foot-pounds per 13mm of plate thickness.
There are two reasons why Alloy 600's impact strength is so impressive. First, the alloy is very light – parts made from Alloy 600 are 40% lighter than parts made from comparable metals. Second, this strength remains constant over a wide temperature range. While metals typically become brittle at low temperatures, this is not the case with INCONEL Alloy 600.
Operating Temperatures
INCONEL Alloy 600 resists embrittlement in extremely cold conditions, and maintains its performance even at extremely high temperatures, even after prolonged exposure. This means it is particularly resistant to creep: a type of failure in which a metal part gradually deforms over time, eventually failing completely.
It is important to note that extremely low temperatures can have an impact on some of Alloy 600's properties. For example, cold drawn 600 alloy bar will lose 20% of its tensile strength at low temperatures. However, as mentioned above, its impact strength remains virtually unchanged.
Applications
Given its excellent operating temperature range, it is no surprise that INCONEL 600 alloy is often selected for use in high temperature environments. Its consistently good mechanical properties and stable performance mean that components made with 600 alloy will have a longer service life and be less prone to catastrophic failure. In many cases, it is a safe and cost-effective choice.
This is especially important in applications where conditions are harsh and safety is critical, such as in the chemical processing and petrochemical industries. INCONEL 600 alloy is also the backbone of the nuclear industry.
All in all, INCONEL 600 alloy has an excellent combination of properties in a wide range of conditions. If you would like to learn more about this alloy and its potential applications in your next project, please contact us.
