Determination of Carbon and Sulfur in Tungsten Carbide (CS844)

Importance of the Topic

Tungsten carbide is widely used in cutting tools, abrasives and wear-resistant parts due to its extreme hardness and toughness. Accurate determination of carbon content ensures proper carburization and binder ratio in cemented carbides, while low-level sulfur analysis is essential to assess material purity and avoid performance issues.

Objectives and Overview of the Article

This application note describes a robust procedure for the simultaneous or separate determination of carbon and sulfur in tungsten carbide using a CS844 series elemental analyzer. It outlines sample preparation, blank correction, calibration/drift protocols and sample analysis to achieve precise and reliable results.

Methodology

The overall workflow includes blank measurements, calibration/drift correction and sample runs. Key steps:

• Sample preparation: crush tungsten carbide to a uniform fine powder.
• Blank determination: run at least three blanks using copper and iron chip accelerators (carbon-only mode) or iron powder, V2O5 and LECOCEL (sulfur mode).
• Calibration/drift correction: measure certified reference materials (WC for carbon, steel chip for sulfur) in triplicate and apply drift correction per instrument manual.
• Sample analysis: weigh ~0.25 g of sample, add appropriate accelerator, and run under constant furnace power, monitoring integration parameters for carbon and sulfur.

Used Instrumentation

The procedure employs a LECO CS844 series carbon/sulfur analyzer equipped with a high-temperature furnace and autosampler. Crucibles (528-018 or 528-018HP), copper and iron chip accelerators, iron powder with V2O5, LECOCEL combustion aid and certified reference materials (501-123 WC, steel chip) are used for sample and calibration runs.

Main Results and Discussion

Typical repeatability for a 6.26 % C reference material is s = 0.01 %. Simultaneous carbon and sulfur analysis of the same WC sample yields 6.27 % C (s = 0.009) and 0.0024 % S (s = 0.0001). These values demonstrate high precision for carbon and sensitive detection limits for sulfur, suitable for stringent quality control.

Benefits and Practical Applications

Reliable carbon measurement confirms complete carburization and correct WC/binder ratio. Sulfur determination at the ppm level detects trace impurities that can compromise material performance. The method’s automation and fast cycle times support high-throughput manufacturing environments and laboratory QA/QC operations.

Future Trends and Opportunities

Advances may include further lowering detection limits, integration with automated sample loaders and robotics, real-time data processing with AI-driven drift correction, and coupling with complementary techniques (e.g., gas chromatography) for multi-element profiling in hard materials.

Conclusion

The LECO CS844 method provides a streamlined, high-precision approach for carbon and sulfur analysis in tungsten carbide. Its robust calibration, simple sample preparation and simultaneous dual-element capability make it ideal for industrial quality control and research laboratories.