Oxygen, Nitrogen, and Hydrogen Determination in Refractory Metals*

Significance of the Topic

Determining oxygen, nitrogen and hydrogen content in refractory metals is essential for controlling mechanical properties and ensuring material performance in critical applications such as aerospace, nuclear and medical devices.

Objectives and Study Overview

This application note outlines a validated procedure for simultaneous determination of O, N and H in refractory metals (Ti, Zr, W, Mo, Ta, Nb, Hf) using the LECO TCH600 inert gas fusion analyzer. It covers sample preparation strategies, instrument parameters, calibration routines and typical analytical results for both solid and powder/chip samples.

Methodology and Instrumentation

This protocol employs inert gas fusion with infrared detection and thermal conductivity detection. Key steps include:

• Sample Preparation: Filing (abrading) of solid samples to remove contamination for O, N and H without introducing hydrogen. Powder/chip samples are encapsulated in tin capsules.
• Accessories: Graphite crucibles, graphite powder, LECO nickel baskets, tin capsules for powders/chips.
• Instrument Parameters: Three outgas cycles; delays of 20 s analysis, integration delays (5 s for O, 15 s for N, 10 s for H); furnace power settings (Outgas at 6000 W, analysis at 5200 W); purge times and low-power clean cycles.
• Calibration and Drift Correction: Performed with certified reference materials (LECO, NIST) covering typical concentration ranges, using repeated runs (≥5) to establish blank and calibration curves.

Main Results and Discussion

Typical analyses demonstrate high precision and accuracy:

• Titanium alloys: O ≈ 0.267% (s = 0.0016), N ≈ 0.0170% (s = 0.0004), H ≈ 12 ppm (s = 0.5 ppm).
• Zirconium alloys: O ≈ 0.131% (s = 0.0004), N ≈ 0.0028% (s = 0.0001), H ≈ 20 ppm (s = 0.5 ppm).
• Tantalum powder: O ≈ 0.206% (s = 0.001), N ≈ 0.0045% (s = 0.0003), H ≈ 38 ppm (s = 1 ppm).

Results indicate excellent repeatability and low detection limits, enabling reliable impurity profiling.

Benefits and Practical Applications

• Simultaneous multi-element determination reduces analysis time.
• Minimal sample preparation prevents contamination artifacts.
• High throughput and semi-automatic operation suit QA/QC and research workflows.
• Versatile for various refractory metals and alloys.

Future Trends and Potential Applications

Continued development may focus on:

• Enhanced automation with robotic sample loading.
• Reduced sample size and microanalysis capabilities.
• Integration of advanced data analytics for real-time quality control.
• Expansion to complex alloy systems and new refractory materials.

Conclusion

The LECO TCH600 inert gas fusion method provides a robust, reproducible approach for determining oxygen, nitrogen and hydrogen in refractory metals. Its reliability and efficiency make it a valuable tool for both industrial quality assurance and advanced materials research.

Reference

• ASTM E1409, E1937, E1447 standard methods for inert gas fusion analysis.
• LECO and NIST certified refractory metal reference materials.