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Microform Calibration Uncertainties of Rockwell Diamond Indenters
J F Song1, F F Rudder1, T V Vorburger1
1National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
Summary
Geometric variations in Rockwell diamond indenters cause significant hardness testing discrepancies. This study calibrates indenter geometry using traceable standards, improving measurement uncertainty and unifying hardness testing globally.
Area of Science:
- Metrology
- Materials Science
- Mechanical Engineering
Background:
- Rockwell hardness testing is crucial for material characterization.
- Significant international discrepancies exist in Rockwell hardness test results.
- Indenter geometry variations are identified as the primary cause of these differences.
Purpose of the Study:
- To calibrate the microform geometric parameters of Rockwell diamond indenters.
- To establish traceability to fundamental standards for indenter calibration.
- To quantify measurement uncertainty in indenter geometry.
Main Methods:
- Utilized a stylus instrument for microform geometric calibration.
- Employed a series of calibration and check standards.
- Applied ISO and NIST guidelines for uncertainty calculation and reporting.
Main Results:
- Achieved traceable calibrations for indenter parameters.
- Quantified expanded uncertainties: ±0.3 μm (radius), ±0.01° (cone angle), ±0.025° (axis alignment).
- Developed procedures for measuring profile deviation, flank straightness, surface roughness, and tip shape.
Conclusions:
- The calibration method quantifies indenter geometry uncertainty, uniformity, and reproducibility.
- This approach enables unification of Rockwell hardness standards through fundamental measurements.
- Reduces reliance on performance comparisons for standard harmonization.
