EDXRF analysis of cast iron composition with ARL QUANT’X Spectrometer

Significance of the Topic

Cast iron alloys, defined by their high carbon content (1.8–4.0% w/w), play a vital role in industries ranging from automotive to construction. Precise control of elemental composition, particularly carbon, determines mechanical properties such as hardness, ductility, and wear resistance. Reliable, rapid, and non-destructive analytical methods are essential for quality control, research, and process optimization.

Study Objectives and Overview

This application note demonstrates the use of the Thermo Scientific ARL QUANT’X EDXRF Spectrometer, equipped with a graphene-window SDD500G detector, for quantitative analysis of cast iron. The primary goals are to establish calibration curves for key elements (C, Si, P, S, Cr, Mn, Ni), evaluate linearity and matrix effects, and assess repeatability across a range of measurement conditions.

Methodology and Instrumentation

Instrumentation:

• ARL QUANT’X EDXRF Spectrometer with 50 W/50 kV rhodium anode and 9-position filter wheel
• Silicon drift detector (SDD500G) featuring a 0.9 µm graphene window for enhanced detection of low-energy X-rays (Z ≥ 6)
• Sample spinner, 10/20-position changer, and capability to operate in air, helium, or vacuum (vacuum used here)

Analytical Conditions:

• Low Za: 4 kV excitation, no filter, 600 s live time for light elements (C, Si, P, S)
• Mid Za: 16 kV excitation, thin Pd filter, 120 s live time for heavier elements (Cr, Mn, Fe, Ni)

Calibration and Sample Preparation:
Eight VASKUT certified reference materials were ground and polished using 120-grit Al₂O₃ on a circular sander. Calibration curves covered concentration ranges from 0.01% to 3.89% w/w, with single influence coefficients applied for Si and Ni to correct minor matrix effects.

Main Results and Discussion

Carbon Kα peaks were clearly resolved in the 0.16–0.38 keV region after linear background subtraction. All calibration curves exhibited strong linearity (R² ranging from 0.9197 for C to >0.992 for other elements) and low RMSE (<0.16% w/w). Repeatability tests on the VASKUT 185 standard (3.28% C) across live times of 20–600 s delivered relative standard deviations below 5%, confirming robust precision even at short measurement durations.

Benefits and Practical Applications

The ARL QUANT’X EDXRF approach offers:

• Non-destructive, simultaneous multi-element quantification
• Capability to detect light elements (carbon) without chemical combustion
• Simple calibration workflows with minimal matrix corrections
• High throughput suitable for production-line quality control and laboratory research

Future Trends and Potential Applications

Further enhancements may include automated sample handling for high-throughput screening, expanded calibration libraries for diverse ferrous alloys, integration with process control systems for in-line monitoring, and hybrid analytical platforms combining EDXRF with portable or benchtop techniques for complementary insights.

Conclusion

The Thermo Scientific ARL QUANT’X EDXRF Spectrometer, when equipped with an ultra-thin graphene window detector, provides a fast, accurate, and repeatable solution for comprehensive cast iron compositional analysis. Its ability to quantify both light and heavy elements with minimal sample preparation makes it an attractive tool for industrial QA/QC and academic research.