Room-temperature impact toughness: In the annealed state (the most common heat treatment condition for Incoloy 800), the alloy has excellent room-temperature impact toughness. Its Charpy V-notch (CVN) impact energy is generally ≥ 150 J (110 ft-lb). This is attributed to its stable face-centered cubic (FCC) austenitic microstructure, which has good ductility and can effectively absorb impact energy by inhibiting the propagation of microcracks.
High-temperature impact toughness: In high-temperature environments below 800°C (1472°F), Incoloy 800 maintains relatively high impact toughness, with CVN impact energy still above 100 J. As the temperature exceeds 900°C (1652°F), the alloy's grain may grow slightly, leading to a gradual decrease in impact toughness, but it still meets the basic requirements of high-temperature structural components.
Effect of impurity elements: Trace impurity elements (such as sulfur, phosphorus) will reduce the impact toughness of Incoloy 800. Therefore, industrial-grade Incoloy 800 strictly controls the content of harmful impurities to ensure stable toughness performance.
2,Is it suitable for low-temperature service environments?
Mild low-temperature range (-20°C to 0°C, -4°F to 32°F): In this temperature range, Incoloy 800 can maintain good impact toughness, with CVN impact energy remaining above 120 J. It can be used for components that bear low dynamic loads, such as pipeline connectors and flanges in low-temperature fluid transportation systems.
Medium and low-temperature range (-50°C to -20°C, -58°F to -4°F): The impact toughness of the alloy begins to decline moderately in this range, but it still avoids brittle fracture under static load conditions. However, it is not recommended for components that bear high dynamic impact loads, because the risk of brittle fracture will increase significantly.
Cryogenic range (below -50°C, -58°F): Incoloy 800 is not suitable for cryogenic service in this range. As the temperature drops sharply, the mobility of dislocations in the austenitic matrix decreases, the alloy's ductility decreases significantly, and the impact toughness drops to below 50 J, which is prone to brittle fracture under external force. For cryogenic applications (such as liquefied natural gas (LNG) equipment), specialized cryogenic alloys (e.g., Incoloy 800H, Inconel 625) with optimized components are more appropriate.
