Thermal Diffusivity Characteristics of the IN718 Alloy Tested with the Modified Pulse Method

Area of Science:

• Materials Science
• Thermodynamics
• Solid State Physics

Background:

• Alloy 718 is a critical material in high-temperature applications.
• Accurate thermal property data is essential for predicting performance and preventing failure.
• Existing thermal diffusivity data for Alloy 718 may have limitations at extreme temperatures.

Purpose of the Study:

• To determine the temperature characteristics of thermal diffusivity for Alloy 718.
• To evaluate the modified pulse method (MPM) for measuring thermal properties.
• To compare experimental results with established databases and identify temperature-dependent anomalies.

Main Methods:

• Utilized the modified pulse method (MPM) for thermal diffusivity measurements.
• Conducted experiments on Alloy 718 samples over a temperature range of 20-900 °C.
• Performed double heating cycles with a two-week interval to assess reproducibility.

Main Results:

• Good correlation with NPL & ASM recommendations and MPDB data was observed between 300-500 °C during the first heating.
• Significant deviations were noted below 300 °C, potentially linked to the electron component of conductivity.
• A distinct minimum above 700 °C suggests a possible influence of delta phase precipitation.

Conclusions:

• The modified pulse method (MPM) is effective for measuring Alloy 718 thermal diffusivity, particularly between 300-500 °C.
• Deviations at lower temperatures highlight the role of electronic conductivity.
• The observed minimum at higher temperatures warrants further investigation into phase precipitation effects.