ThePipingMart Blog Grades 903 Incoloy Alloy (UNS N19903) – Composition, Properties and Uses

903 Incoloy Alloy (UNS N19903) – Composition, Properties and Uses

Incoloy 903

UNS N19903 is an alloy with various uses due to its combination of excellent mechanical and physical properties. This versatile alloy is resistant to wear, heat, and corrosion, making it well-suited for many applications. Keep reading to learn more about what Incoloy 903 is and how it can be used.

903 Incoloy Composition

Incoloy Alloy 903 is a nickel-based superalloy containing iron, chromium, manganese, silicon, aluminium and titanium. The exact composition varies depending on the manufacturer but typically contains around 32% nickel, 14% chromium, 3% manganese, 3% silicon and 1.5% titanium.

Element Content (%)
Iron, Fe 42
Nickel, Ni 38
Cobalt, Co 15
Niobium, Nb 3
Titanium, Ti 1.4
Aluminum, Al 0.9

903 Incoloy Chemical Properties

The presence of chromium gives Super Alloy Incoloy 903 superior oxidation resistance compared to other alloys in its class. It also has excellent resistance to sulfidation and carburization at high temperatures.

903 Incoloy Mechanical Properties

The alloy’s mechanical properties make it suitable for various applications where strength or hardness are essential. Incoloy 903 has a tensile strength of over 1000MPa when heat treated correctly, and a yield strength of 900MPa when hot or cold worked. It also has good creep resistance at temperatures up to 1150°C (2100°F).

Properties Metric Imperial
Tensile strength (precipitation hardened) 1310 MPa 190000 psi
Yield strength (@ strain 0.200 %, precipitation hardened) 1100 MPa 160000 psi
Elastic modulus (@ 0°C/32°F) 146.8 GPa 21290 ksi
Poisson’s ratio (@ 250°C/482°F) 0.226 0.226
Elongation at break (precipitation hardened) 14% 14%

903 Incoloy Physical Properties

In addition to its superior mechanical properties, Incoloy 903 also offers high levels of workability with good formability and weldability thanks to its low carbon content. Due to its hardness levels, the alloy can be machined using standard cutting tools, grinding wheels, or abrasive discs with minimal tool wear.

Properties Metric Imperial
Density 8.25 g/cm³ 0.298 lb/in³
Melting point 1385°C 2525°F

903 Incoloy Thermal Properties

Properties Metric Imperial
Thermal expansion coefficient (@ 25-427°C/77-801°F) 7.65 µm/m°C 4.25 µin/in°F
Thermal conductivity 16.7 W/mK 116 BTU in/hr.ft².°F

903 Incoloy Uses

Due to its combination of good physical and chemical properties, Incoloy 903 is widely used in a variety of applications, including furnace components such as retorts and tubular structures for petrochemical industry processes; turbine blades for aircraft engines; blades for steam turbines; components for power plants; pump parts; fasteners; valve stems; nuclear fuel rods; nozzles; shafts; bushings; stud bolts; nuts and cladding materials for nuclear reactor vessels.

Corrosion Resistance

One of the key advantages of using this alloy is its excellent corrosion resistance in both acidic and alkaline environments and reducing atmospheres such as hydrogen sulfide gas or sulfur dioxide gas which have been known causes of metal fatigue failure in other alloys. The addition of aluminium helps give the alloy enhanced resistance against pitting corrosion compared with similar alloys while still retaining good ductility levels even after long-term exposure in corrosive environments such as seawater or sour crude oil production fields.

Heat Resistance

Incoloy 903 is a highly heat-resistant material used in many industries, including petrochemical processing and power generation. It is incredibly resistant to high temperatures, but this alloy also offers superior oxidation resistance, creep resistance and good tensile strength. It has vastly improved upon the properties of its predecessor alloys, making it a rather popular choice for components expected to come into contact with extreme temperatures or other intense conditions. Because of its qualities, Incoloy 903 can be expensive, but it proves itself through reliability and exceptional resistance capabilities over time.

Heat Treatment

For most applications involving Incoloy 903, the recommended heat treatment process requires solution annealing followed by air cooling or rapid quenching depending on the desired microstructure required for particular application needs. This process helps achieve the best combination of metallurgical properties without sacrificing performance capabilities.


Incoloy 903 has quickly become a popular material choice for machining due to its increased toughness and good corrosion resistance. This alloy is often used in applications where exposure to high temperature or corrosion is a likely occurrence, as it can withstand pressure and temperature better than many other metals available today. Special consideration must be taken when machining Incoloy 903 to keep temperatures from climbing too high and burning out tooling prematurely. With proper technique, this alloy offers the efficiency of production and long-term reliability that industrial companies need from their machined components.


Incoloy 903 welding is a complex but necessary process for many industries. Welding this alloy requires specific temperatures that must be carefully maintained and monitored to get maximum results. It also demands a higher skill level from welders as the metallurgy of Incoloy 903 is more complex than other commonly used alloys. Furthermore, welders need to keep closer track of both their tools and the job quality due to the more challenging weld pool action inherent when working with this alloy. Incoloy 903 welding requires greater attention and expertise but can deliver superior results for those willing to rise to its challenge.


In conclusion, Incoloy9 03 is an exceptionally versatile superalloy due to its excellent mechanical, physical, chemical, corrosion, heat treatment, machining, welding – allergenicity characteristics that make it ideal for many applications. With proper care taken during manufacture, maintenance & operation, this superalloy can provide reliable service life expectancy. Additionally, if manufacturing standards are adhered to too strictly, there should be no need for additional post–fabrication treatments making it cost-effective compared with some other competing materials. Therefore if you require a durable superalloy that can withstand extreme conditions, you should consider investing in an Incolay9 03 product.

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