Detailed Chemical Composition Range of Incoloy 800
Incoloy 800 is a nickel-iron-chromium austenitic alloy, whose chemical composition is strictly standardized by international specifications such as ASTM B409 (for plate, sheet, and strip), ASTM B408 (for bars and forgings), and UNS N08800. The detailed content range of its key elements (including nickel, chromium, iron, carbon, manganese, etc.) is defined as follows, with all values expressed in weight percentage (wt%):
| Element | Content Range (wt%) | Key Function in the Alloy |
|---|---|---|
| Nickel (Ni) | 30.0 – 35.0 | The core austenite-stabilizing element. It enhances the alloy's high-temperature creep resistance, toughness, and corrosion resistance in reducing environments. The moderate nickel content balances performance and cost, avoiding the high material cost caused by excessive nickel addition. |
| Chromium (Cr) | 19.0 – 23.0 | A critical element for corrosion and oxidation resistance. It forms a dense, adherent chromium oxide film (Cr₂O₃) on the alloy surface at high temperatures, which effectively blocks the intrusion of oxygen, carbon, and corrosive media. This component is the basis for the alloy's excellent high-temperature oxidation and carburization resistance. |
| Iron (Fe) | Balance (typically 39.5 – 49.5) | The base matrix element of the alloy. It reduces the overall alloy cost while cooperating with nickel and chromium to maintain the stability of the austenitic structure. |
| Carbon (C) | ≤ 0.10 | Strictly controlled at a low level to avoid the precipitation of chromium carbides (Cr₂₃C₆) at grain boundaries during welding or heat treatment. This effectively prevents intergranular corrosion and ensures the structural integrity of welded components in corrosive environments. |
| Manganese (Mn) | ≤ 1.50 | Acts as a deoxidizer during smelting, improving the casting and forging processability of the alloy. It also slightly enhances the alloy's strength without significantly reducing its ductility. |
| Silicon (Si) | ≤ 1.00 | A deoxidizing and desulfurizing agent in the smelting process. It helps improve the alloy's fluidity during casting and contributes to the formation of a continuous oxide film, enhancing high-temperature oxidation resistance. |
| Aluminum (Al) | 0.15 – 0.60 | Works with titanium to form fine precipitates (such as Ni₃Al, Ni₃Ti) at high temperatures, which can pin the grain boundaries and improve the alloy's high-temperature creep strength and structural stability. |
| Titanium (Ti) | 0.15 – 0.60 | Cooperates with aluminum to play a precipitation strengthening role. It also has a strong affinity for carbon, which can form titanium carbides and reduce the risk of chromium carbide precipitation, further suppressing intergranular corrosion sensitivity. |
| Copper (Cu) | ≤ 0.75 | A trace impurity element, with its content strictly limited to avoid adverse effects on the alloy's high-temperature performance and weldability. |
| Sulfur (S) | ≤ 0.015 | A harmful impurity. Its low content ensures the alloy's toughness and resistance to intergranular cracking, especially in high-temperature service conditions. |
| Phosphorus (P) | ≤ 0.030 | Another controlled impurity element. Limiting its content prevents the occurrence of low-temperature brittleness and improves the alloy's processing performance. |
