According to the main matrix elements of the alloy, high-temperature alloys can be mainly divided into three categories: nickel-based, cobalt-based, and iron-based.
The following are the main characteristics of various types of alloys:
1. Characteristics of nickel-based high-temperature alloys
Nickel-based superalloys are known for their excellent structural stability and are not prone to the generation and precipitation of harmful phases. It can solid-solubilize more alloying elements, thereby obtaining extremely high high-temperature strength. Especially after adding chromium, nickel-based alloys show the best anti-oxidation properties. Although slightly inferior to cobalt-based alloys in terms of resistance to hot corrosion and thermal fatigue, nickel-based superalloys are still the preferred material in high-temperature environments.
2. Characteristics of cobalt-based high-temperature alloys
The structural stability of cobalt-based superalloys is slightly inferior to that of nickel-based alloys, but their solid solution-strengthening capabilities are equally excellent. Cobalt-based alloys have excellent resistance to hot corrosion and thermal fatigue and are particularly suitable for use in harsh corrosive environments. After adding chromium, the oxygen resistance of cobalt-based alloys is better than that of iron-based alloys, but it is still slightly insufficient compared to nickel-based alloys. Cobalt-based alloys are more suitable for working environments under high temperatures and low-stress static conditions.
3. Characteristics of iron-based high-temperature alloys
Iron-based superalloys have relatively low structural temperature stability, fewer alloying elements in solid solution, and are prone to precipitation of harmful phases. Therefore, the high-temperature strength, oxidation resistance, and hot corrosion resistance of iron-based alloys are relatively low. However, iron-based alloys are still used in certain specific areas due to their low cost.