Nickel-chromium based alloys, great resistance to carburization and oxidation in high temperature capacity solutions – that sums up the Austenitic SS 800 and its types SS 800H and 800 HT. Similar to nickel-steel alloys, SS 800H contains increased carbon and additional (upto) 1.20% aluminum and titanium in alloy 800HT.
Austenitic SS 800 was modified into alloy 800H for material purposes. The Austenitic SS 800/ H/ HT is dually certified and has property combinations of both forms. Embrittlement resistance occurs through sigma phase and chloride stress corrosion cracking takes place due to high nickel content.
Austenitic SS 800/ H/ HT grades are ductile due to the long term use of the composition. Austenitic SS 800 has its temperature range from room temperature-590°C. For usage above 590°C, Austenitic SS 800H/ 800HT works best. These grades exhibit exceptional creep resistance properties and seldom fail, however lengthy the duration. SS 800H/ 800HT resist embrittlement because of the composition and titanium. Titanium stabilizes the carbides.
Aluminum in grade 800HT is used to form intermetallic compounds during precipitation, which result in increased metal strength. Aluminums tighten improving oxidation resistance.
Utilized in applications that cross 1100°F, Austenitic SS 800/ SS 800H/ 800HT finely manage creep resistance and rupture. Be it hot or cold worked, precise execution is key for grade efficiency. The deformation needs to be under 5% within the temperature range around 850-1100°C. If increased deformation, the temperature must be at 950°-1100°C.
On observation, lesser temperature than the precipitated degree means loss of metal strength. Intense heat treatment is required to retain normal strength. For corrosion and creep resistance properties of the Austenitic SS 800 grade, the solution is cold working. If the deformation still persists, then the metal needs annealing to remove brittleness.
Incoloy 800/ 800H/ 800HT are nickel-iron-chromium alloys with good strength and excellent resistance to oxidation and carburization in high-temperature exposure. These nickel-steel alloys are identical except for the higher carbon level in alloy 800H, and the additional (upto) 1.20% aluminum and titanium in alloy 800HT.
Incoloy 800, slightly modified into Incoloy 800H, was to control carbon (0.05-0.10%) and grain size to optimize stress rupture properties. Incoloy 800HT, with combined titanium and aluminum levels (0.85-1.20%) ensure high temperature properties.Incoloy 800 is applied in temperatures up to 1100°F. Alloys 800H/ 800HT are used in temperatures above 1100°F. The chemical balance allows the nickel-steel alloy to exhibit excellent resistance to nitriding atmospheres.
vINCOLOY alloys 800H/ 800HT products function at optimum in high temperature properties. Carbon makes its contribution after the annealing process, resulting in a large grain size which further contributes to strength and resistance to creep and rupture at high temperatures.
Heating INCOLOY alloy 800/ 800H/ 800HT must be performed in a low-sulfur atmosphere. Open heating must be with low-sulfur fuel, and the furnace atmosphere must be maintained in a reducing condition to prevent excessive oxidation. The high nickel-chromium contents in alloy 800H/ 800HT results sulﬁdation and the nickel content increases the nitriding resistance.
Incoloy 800HT is not subjected to embrittlement even after long periods of usage in the 1200-1600°F range. In the annealed condition, the tensile strength to yield strength ratio of Incoloy 800/ 800H/ 800HT is high, typically greater than two. Large amounts of cold work can be performed before annealing.
The mechanical properties of INCOLOY alloys 800H/ 800HT are useful in applications involving long-term exposure to elevated temperatures and corrosive atmospheres. APPLICATIONS:
- Heat exchangers
- Heating elements
- Carburizing equipment
- Power generation equipment
- Petroleum refining equipment
- Chemical and petrochemical processing
- Ammonia effluent cooler
- Process piping
- Furnace components
- Hydrocarbon cracking
- Pressure vessels