High precision nickel alloy analysis

Significance of the topic

The precise quantification of trace metals in nickel superalloys is critical for aerospace components where material performance and safety are paramount. Glow discharge mass spectrometry (GD-MS) combines multielement capabilities and minimal matrix effects, making it well suited for quality control in high-value alloys. The recent upgrade to a modulated (pulsed) discharge on the Thermo Scientific™ Element™ GD Plus offers potential improvements in measurement stability and spot-to-spot precision.

Objectives and study overview

This work aims to evaluate the analytical performance of the Element GD Plus GD-MS in pulsed discharge mode for trace element analysis of a certified nickel superalloy (CRM BAS346A, IN100). Key goals include:

• Assessing precision across multiple spots and runs
• Comparing reproducibility with continuous DC mode
• Investigating the impact of source part exchanges (anode cap, flow tube)

Methodology

CRM BAS346A samples were prepared by wet grinding on 80-grit SiC paper, rinsed with deionized water, soaked in iso-propanol, and dried under a nitrogen stream. Sixteen replicate analyses were performed with the following GD-MS conditions:

• Discharge voltage: 800 V
• Pulse frequency: 4 kHz, pulse width: 40 µs
• Average discharge current: ~15 mA
• Presputter time: 6 min; data acquisition time: 6 min
• Anode: stainless steel consumables

Used instrumentation

• Thermo Scientific™ Element™ GD Plus glow discharge mass spectrometer
• SiC grinding media and sample cleaning accessories
• Nitrogen drying and iso-propanol rinsing setup

Main results and discussion

Repeated runs demonstrated excellent reproducibility for most trace elements, with relative standard deviations (RSD) typically below 2% under optimized conditions. Key observations include:

• Minimal difference in RSD between pulsed and continuous modes
• Best precision achieved when source parts remain in place (up to 2 hours sputtering, equivalent to ~10 sample runs)
• Anode cap exchange had negligible effect on precision
• Flow tube exchange increased variability slightly but remained within acceptable limits
• Long-term stability test (4 h on a single spot) stayed within a 10% concentration variation, half of which arose from crater depth effects

Practical benefits and applications

The pulsed discharge GD-MS method delivers:

• High precision trace metal profiles in nickel alloys for aerospace QA/QC
• Reduced sputter rates for improved spatial resolution and minimized crater effects
• Robust operation with routine source maintenance (daily flow tube exchange)

Future trends and potential applications

Ongoing developments may include:

• Further optimization of pulse parameters for diverse matrices
• Automated workflows for high-throughput alloy screening
• Integration with advanced data analytics for real-time quality assurance
• Extension of pulsed GD-MS to other conductive and non-conductive materials

Conclusion

The Thermo Scientific™ Element™ GD Plus in pulsed discharge mode offers trace element determination in nickel superalloys with precision and stability comparable to or exceeding continuous DC operation. Its low sputter rate and consistent performance support rigorous quality control in aerospace materials.

References

No additional references provided.