All four types belong to nickel-based or iron-nickel-based corrosion/heat-resistant alloys, and their core application scenarios are working conditions that stainless steel cannot handle in high-temperature or highly corrosive environments. In simple terms: NO6600 is a "basic grade for high-temperature oxidation resistance", NO6625 is an "all-rounder with high strength and strong corrosion resistance", NO8811 is an "expert in high-temperature creep resistance", and NO8825 is a "versatile alloy for acid resistance". The following is a comparison of key properties and applications: · NO6600 (Inconel 600): Resistant to high-temperature oxidation and chloride. With a nickel content of ≥72%, it exhibits excellent oxidation resistance and resistance to chloride ion stress corrosion cracking below 700°C, but poor sulfidation resistance. It is mainly used in high-temperature working conditions such as heat exchangers and nuclear reactor components.· NO6625 (Inconel 625): An all-rounder for extreme environments. Strengthened by the addition of molybdenum (9%) and niobium, it delivers outstanding resistance to pitting corrosion, crevice corrosion and high-temperature oxidation. It combines ultra-high strength (tensile strength >827MPa) and good fatigue resistance. Used in extremely harsh environments such as marine engineering and aero-engines.· NO8811 (Incoloy 800HT): Specialized for high-temperature creep resistance. A high-performance version of 800H, it achieves coarse grains through composition adjustment, providing optimal creep rupture resistance above 600°C. Specialized for high-temperature pressure-bearing components in nuclear energy, petrochemical heating furnaces and other fields.· NO8825 (Incoloy 825): Acid and corrosion resistant. With a relatively high iron content (approximately 42%), as well as added molybdenum and copper, it performs excellently in strong acid environments such as sulfuric acid and phosphoric acid, as well as seawater. Used in chemical processing equipment, sour oil and gas wells, etc.