Incoloy 825 bolts are known for their strong mechanical properties and reliable performance in aggressive environments. These bolts are used in chemical plants, marine applications, and power plants where resistance to heat, pressure, and corrosion is critical. Their strength and stability make them suitable for both high and low-temperature service.
These bolts are made from Incoloy 825, a nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. This combination offers excellent resistance to various forms of corrosion, including pitting, crevice corrosion, and stress corrosion cracking. Incoloy 825 bolts follow different ASTM standards depending on the form and use, such as ASTM B425 and ASTM B564.
Mechanical Properties of Incoloy 825 Bolts
Incoloy 825 bolts are tough and durable. Their strength comes from the solid solution of nickel and iron, along with added elements like molybdenum and titanium. These elements improve the mechanical stability and corrosion resistance of the bolts.
Tensile Strength
The average tensile strength of Incoloy 825 bolts is around 585 MPa (85 ksi). This gives them the ability to withstand high levels of tension. It ensures that the bolts can hold parts tightly without breaking under normal working loads. Their stability under tensile stress makes them dependable in structural and pressure-based systems.
Yield Strength
The yield strength is about 220 MPa (32 ksi). This refers to the stress point at which a bolt begins to deform permanently. Incoloy 825 bolts handle moderate loads well without bending, or losing their shape. This makes them ideal for systems that operate under constant or fluctuating pressure.
Elongation
Incoloy 825 bolts have an elongation rate of around 30%. This reflects their ability to stretch or deform without breaking. It is a key property for applications that involve vibration, movement, or thermal expansion. A high elongation value helps absorb shock and stress, reducing the risk of failure.
Hardness
These bolts have a moderate hardness, usually between 150 and 200 HB (Brinell Hardness). This means they can resist wear and tear during installation and operation. At the same time, they are not too hard to machine or cut, allowing easy shaping and fitting when needed.
Creep and Rupture Resistance
Incoloy 825 bolts maintain strength over time under high heat and pressure. They resist slow deformation (creep) and sudden breakage (rupture) even during long exposure to elevated temperatures. This makes them reliable in heat exchangers, furnaces, and other thermal systems.
ASTM Standards for Incoloy 825 Bolts
Different ASTM standards guide the production and use of Incoloy 825 bolts. These standards ensure the bolts meet specific strength, hardness, and chemical composition requirements.
ASTM B425
This standard covers the specification for Incoloy 825 in the form of seamless pipes and tubes, but it also applies to bar, rod, and wire used to make bolts. It sets the basic chemical and mechanical limits for the alloy, making sure the final product is reliable.
ASTM B564
ASTM B564 is for nickel alloy forgings, including Incoloy 825. Bolts made through forging are shaped to exact sizes, and meet strict quality needs. This standard confirms that the mechanical properties are preserved during the forging process.
ASTM B166
Though not used as often for bolts, this standard is important when the bolts are made from cold-drawn wire or hot-rolled bar stock. It helps ensure the raw materials meet hardness and strength requirements. These standards give buyers and engineers confidence that the bolts will perform as expected under demanding conditions.
Corrosion Resistance
One of the key features of Incoloy 825 bolts is their high corrosion resistance. The mix of nickel, chromium, and molybdenum protects the bolts from a wide range of acids and salts. This includes sulfuric acid, phosphoric acid, nitric acid, and seawater.
They resist pitting and crevice corrosion even in chloride-rich environments. This makes them useful in marine and offshore systems, as well as in pollution control equipment. The added copper improves resistance to sulfuric and phosphoric acid, while titanium helps resist stress corrosion cracking.
Thermal Performance
Incoloy 825 bolts can be used in systems where the temperatures range from cryogenic levels to about 540°C (1000°F). They don’t become brittle at low temperatures and don’t lose strength quickly at high temperatures. This makes them useful in piping systems, heaters, condensers, and pressure vessels.
They also maintain their mechanical properties in environments with repeated heating and cooling cycles. The bolts do not crack or lose grip, even when exposed to thermal stress.
Applications of Incoloy 825 Bolts
Because of their strong mechanical and anti-corrosion features, Incoloy 825 bolts are used in many industrial fields.
Chemical Processing – for handling strong acids and mixed chemical flows.
Marine Engineering – in shipbuilding, offshore rigs and seawater systems.
Power Generation – in nuclear and fossil fuel plants, where heat and stress are high.
Pollution Control – for flue gas scrubbers and waste treatment systems.
Oil and Gas Industry – for pumps, valves, and pipelines under high pressure and temperature.
Pharmaceutical Equipment – due to their resistance to contamination and corrosion.
Final Thoughts
Incoloy 825 bolts are made to last in tough environments. Their strength, corrosion resistance, and stable performance under heat make them reliable in industries that demand safety and efficiency. When bought under trusted ASTM standards like B425 and B564, these bolts offer consistent quality and performance.
Their mix of mechanical properties and resistance to harsh chemicals makes them a preferred choice for engineers and plant operators. Whether used in chemical tanks, reactors, heat exchangers, or marine vessels, Incoloy 825 bolts deliver strength and durability.
Related Posts
