Hydrogen Determination in Reactive and Refractory Metals*

Importance of the Topic

Hydrogen content is a critical chemical specification for reactive and refractory metals, particularly titanium and its alloys. Excess hydrogen can form brittle hydride phases that reduce ductility and promote stress-corrosion cracking or catastrophic failure in high-performance applications such as aerospace, medical implants, and military components. Reliable and precise hydrogen determination is therefore essential for quality control, materials qualification, and failure prevention in industry and research.

Objectives and Study Overview

This application note documents a validated procedure for hydrogen determination in reactive and refractory metals using the LECO RH600 and TCH600 hydrogen determinators. The goals are to present sample preparation practices, instrument configuration, calibration and blanking approaches, and example performance data for solid samples (pins, chips), powders, and tin-capsule-contained materials. ASTM E1447 is cited as the method reference.

Methodology

Summary of the analytical approach:

• Technique: Inert-atmosphere combustion (electrode furnace) with helium carrier gas and infrared detection of H-containing gases.
• Sample mass: Typically 0.15–0.30 g for routine solid samples. A 1.0000 g entry is used to determine instrument blank.
• Sample forms: Solid pins and chips are placed directly in a graphite crucible with tin flux (two tin pellets). Powdered or small chip samples can be loaded in open tin capsules or transferred via a funnel to limit atmospheric exposure.
• Preparation: Avoid overheating during sectioning (prefer shearing); remove surface contamination by filing, acetone rinse, and air drying; handle cleaned parts with tweezers to prevent contamination.
• Blanking and calibration: Perform at least three blank runs and three runs per calibration or drift-correction standard. Recommended calibration materials include LECO titanium standards (502-135, 762-741) or suitable certified refractory metal reference materials.

Used Instrumentation

Key instrument and consumables referenced:

• Instrument: LECO RH600 or TCH600 hydrogen determinator (electrode furnace with helium carrier and IR detector).
• Crucibles and consumables: Graphite crucible (LECO 782-720), tin pellets (LECO 761-739), tin capsules (LECO 501-059 or 502-040) and funnel (LECO 617-997) for powder loading.
• Calibration reference materials: LECO kits 502-135 and 762-741; NIST or equivalent refractory metal reference standards when available.

Main Method Parameters (typical)

Representative instrument settings summarized from the application note:

• Outgas cycles: 3
• Analysis delay: 20 s; integration delay: 15 s
• Minimum analysis time: 60 s; significant digits: 6
• Pre-analyze purge: typically 10 s (longer purge used for manual top load workflows)
• Purge time: 15 s; outgas time: 5 s; outgas cool time: 5 s
• Furnace currents: typical analyze/outgas power in the range of ~800–850 amps (adjustable depending on line voltage and crucible wear)

Main Results and Discussion

Precision and practical performance illustrated by examples in the note:

• Titanium pin standard (LECO 762-741): measured near 42 ppm H with good repeatability (standard deviation ~0.8 ppm), demonstrating robust mid-range sensitivity.
• Titanium pin standard (LECO 502-135): low-level standard near 11 ppm H with precision around 1 ppm, indicating capability to quantify low hydrogen concentrations in titanium.
• Tantalum powder (example powder method, tin capsule): results around 191 ppm H with s ≈ 5.3 ppm, showing the method handles higher-hydrogen refractory powders with acceptable precision.
• Titanium chips (manual top load example): mean ≈ 57 ppm H, s ≈ 2.2 ppm, demonstrating suitability for irregular chip geometries when manual top-load or funnel-assisted transfer is used.

Discussion notes:

• Use of tin pellets as a flux assists hydrogen release and capture during high-temperature fusion, improving recovery and reproducibility.
• Blank control is critical—direct manual insertion significantly increases blank variability and is discouraged. Manual top-load with a funnel or semi-auto capsule analysis reduces atmosphere exposure and improves precision for powders.
• Furnace power settings and electrode life are practical considerations; settings may be adjusted to minimize crucible burn-through or to optimize recovery for different sample matrices.

Benefits and Practical Applications

The described method and instrumentation provide:

• High sensitivity and repeatability for hydrogen in reactive/refractory metals across a practical concentration range (low ppm to hundreds of ppm).
• Flexibility to analyze solids, chips, and powders using direct loading, tin capsules, or funnel-assisted manual top-load procedures.
• Compliance with established practice by referencing ASTM E1447 and using certified calibration standards, supporting quality systems and traceability in production and QA/QC environments.

Future Trends and Potential Applications

Emerging directions and opportunities for hydrogen analysis in metals include:

• Automation and improved sample handling to reduce blank variability and increase throughput (integration with autosamplers and improved capsule-handling workflows).
• Enhanced furnace and detector designs for lower detection limits, faster cycle times, and reduced crucible wear—important for high-throughput industrial labs.
• Advanced calibration strategies and matrix-matched certified reference materials to further improve accuracy for complex alloys and powder blends.
• Integration of data management and LIMS connectivity to support statistical process control and materials traceability in regulated industries (aerospace, medical devices).

Conclusion

The LECO RH600/TCH600 instrument and the described procedures offer a validated, flexible approach for determining hydrogen in reactive and refractory metals. Adherence to careful sample preparation, rigorous blanking/calibration, and appropriate loading technique yields precise and reproducible results across sample types. Proper control of furnace parameters and sample handling is essential to minimize artifacts and ensure accurate hydrogen recovery.

References

1. ASTM E1447 — Standard Test Method for Determination of Hydrogen in Titanium and Titanium Alloys by Inert Gas Fusion.
2. LECO Application Note: Hydrogen Determination in Reactive and Refractory Metals — Instrument RH600 / TCH600, LECO Corporation, Saint Joseph, MI.