Inert Gas Fusion

Extraction Sequence

Heating of the sample occurs in a precisely controlled environment to ensure that all target gases are completely released from the metal matrix. During inert gas fusion, the furnace temperature often exceeds three thousand degrees Celsius, which is sufficient to melt even refractory metals. As the sample liquifies, the oxygen present reacts with the carbon of the graphite crucible to form carbon monoxide.

Nitrogen and hydrogen are released in their elemental form and are swept away by the inert carrier gas. The system uses various traps to remove unwanted byproducts like moisture or dust before the gas reaches the analytical cells. This ensures that the final measurement reflects only the gases that were originally part of the metal sample.

Detection Limit

Accuracy of the results depends on the sensitivity of the infrared and thermal conductivity detectors used in the instrument. For oxygen and carbon monoxide, infrared absorption cells are used to measure the amount of light absorbed by the gas at specific wavelengths. Nitrogen and hydrogen are typically measured using thermal conductivity detectors that sense the change in the gas composition.

Modern inert gas fusion systems can detect these elements at concentrations as low as one part per million. This level of precision is necessary for high performance alloys where even a tiny amount of contamination can lead to material failure or reduced performance. Regular calibration with certified standards is required to maintain this high level of accuracy over time.

Material Integrity

Measuring the gas content provides a clear picture of how the material was processed and how well it was protected from the environment. High oxygen levels in a metal powder can indicate poor atomization conditions or improper storage that allowed for surface oxidation. Excess nitrogen can lead to the formation of brittle nitrides that reduce the toughness of the final part.

By using inert gas fusion, manufacturers can verify that their powders are clean and ready for use in critical additive manufacturing or sintering processes. The data from these tests is often a mandatory part of the material certification package provided to the end user. It serves as a final check on the chemical stability of the alloy before it is converted into a finished component.