1. Material properties
Incoloy metal's core components are nickel (30-35%), chromium (19-23%), and iron (≥39.5%) with an addition of some solid-solution strengthened austenite structure, minor proportions of aluminum, titanium, and silicon. Its structure provides a number of benefits to the material.
Both the Ni and Cr components of the alloy ensure the material has good oxidation resistance around the 550-1000°C range, even in extreme conditions with water vapor and sulfur gas. Add to that the other benefits, and you have a much more valuable material than a standard alloy.
The material, even in an annealed condition, demonstrates exceptional qualities. Incoloy has a tensile strength of ≥520 MPa and yield strength of ≥205 MPa while elongating ≥30% in addition to a balance of ductility and strength, even in high temperatures.
Physical composition of Incoloy 800 is the density of 7.94-8.02 g/cm³., the melting point ranging from 1350-1400°, and the thermal conductivity of, for example, 12.6 W/m·K at room temperature and 26.7 W/m·K at 1000° W/m·K increasing with temperature (12.6-1000 temperature, the 12.6 W/m·K at room W/m·K). The thermal expansion from 0-100°C is 13.7-14.4 µm/m·°C. This expansion is within operational limits for high-temperature thermal cycling environments.
2. Treatment and processing technology
a. Heat Treatment:
1) Annealing: Generally done between 1150° and 1180°. This should be followed by water quenching or rapid airstepping to reduce residual stresses and maximize ductility.
2) Solution Treatment: Sharply cooled after heating from 980° to 1060° to improve microstructure homogeneity and high-temperature creep resistance.
b. Hot Working: Prefer 1000° to 1230°. Working between 650° and 850° should be avoided as this may cause cracking.
c. Cold Working: There is less work hardening, so conventional cold rolling and stamping can be done, but intermediate annealing is needed to recover ductility.
d. Welding: Supports TIG, MIG, as well as manual metal arc welding. Suggested consumables are ERNiCr-3 or ENiCrFe-2. It is critical to control heat input to eliminate intergranular corrosion.
3. Core application areas
a. Chemical and petrochemical
Equipment manufacturing. Used in reactors for sulfuric acid, coolers for nitric acid, fractionating towers, and heat exchangers while enduring strong acid, high temperature, and severe pressure.
Pipeline systems. Replaces stainless steel in chloride-containing media, which greatly extends service life.
b. Energy and power
Fuel power generation. Steam environments over 600°c in superheater, boiler tubes, and turbine blades.
Nuclear power. Used in components and tubes of cooling systems in steam generators of nuclear reactors. Endures radiation and high-temperature water corrosion.
c. Aerospace
Engine components. Manufactures combustion chambers and high-pressure gas and high-temperature gas turbine blades while enduring erosion and severe thermal fatigue.
d. Oil and gas
Deepwater equipment. Used in casing of oil wells and subsea pipelines while enduring severe pressure, high salinity, and hydrogen sulphide corrosion.
4. Comparison of derivative models: Incoloy 800H and Incoloy 800HT
Incoloy 800H and Incoloy 800HT are modifications of Incoloy 800, mainly differing in the content of carbon, aluminum, and titanium, and grain control:
800H: The increased carbon content is up to 0.06-0.10%. The combined aluminum and titanium content is ≥0.85%. The coarse-grained (≥90 μm) structure developed by high-temperature solution treatment greatly enhances creep resistance (>600°C). It is used in heating furnaces and reactors in the petrochemical industry.
800HT: The combined aluminum and titanium content is further increased to 0.85-1.20%. This results in refined grains and the introduction of γ′ phase strengthening, which enhances creep rupture strength. It is designed for ultra-high-temperature equipment, such as aircraft engine combustors, operating at 700-1000°C.
