Both Inconel 718 and Inconel 625 are known for their high-temperature capabilities, but they have slightly different temperature limits based on their compositions and properties.

Inconel 718:
Service Temperature Range: Inconel 718 is known for its excellent high-temperature strength and good oxidation resistance. It can be used in a wide temperature range, typically from cryogenic temperatures up to around 1300°F (704°C).
High-Temperature Strength: Inconel 718 maintains its mechanical properties at elevated temperatures, making it suitable for applications such as gas turbines, jet engines, and other high-temperature environments.

Inconel 625:
Service Temperature Range: Inconel 625 is also capable of performing well at high temperatures. It has a service temperature range typically from cryogenic temperatures up to around 1800°F (982°C).
Corrosion Resistance: Inconel 625 is particularly valued for its excellent corrosion resistance in various environments, including high-temperature applications where resistance to oxidation and pitting are crucial.

Inconel 718 has a service temperature range up to around 1300°F (704°C), offering excellent high-temperature strength and oxidation resistance.

Inconel 625 can withstand temperatures up to around 1800°F (982°C), while also providing exceptional corrosion resistance in harsh environments.

It's important to note that the actual temperature limits may vary based on specific applications and conditions. When selecting between these alloys for a particular application, it's essential to consider the temperature requirements and other factors to ensure optimal performance.