Rockwell hardness test simply explained (comparison with Brinell and Vickers)

The Rockwell hardness test is one of the most commonly used methods to determine material hardness. Unlike the Brinell and Vickers methods, which measure hardness based on the impression area, the Rockwell method determines hardness using the penetration depth of the indenter. A hard metal ball or a diamond cone is used as the indenter. The main advantage of the Rockwell test is its suitability for automation and quick execution, as no optical measurement is required. This makes it ideal for industrial mass production. The process begins with applying a minor load F0 of 98 Newton to compensate for surface irregularities. The major load F1 is then applied, driving the indenter deeper into the material. After removing the major load, only the minor load remains, and the difference in penetration depth is measured, which is used to calculate the hardness value. A diamond cone is used for hard materials, measuring hardness on a scale from 0 to 100, with a maximum penetration depth of 0.2 mm. For softer materials, hard metal balls are used, and the reference depth increases to 0.26 mm. Different scales are employed: HRB for structural steel and brass, HRC for hardened steel, and HRA for thin sheets. Each scale has specific force and hardness value ranges. Accurate calibration is crucial, as values outside the acceptable range require procedural adjustments. Minimum specimen thickness is also important: it must be ten to fifteen times the penetration depth, depending on the indenter type. The distance from the impression to the edge must be at least 1 mm, and the surface must be finely ground to avoid measurement errors. The advantages of the Rockwell method include short testing times and excellent suitability for automation. However, drawbacks include sensitivity to surface impurities and limited depth measurement accuracy for very hard materials, where the Vickers method is more suitable. For heterogeneous materials like cast iron, the Brinell method provides better results. A summary table outlines the pros and cons of each method. 00:00 How is the Rockwell hardness test carried out? 01:28 How is Vickers hardness calculated? 03:06 Testing with diamond cones 05:10 Testing with carbide balls 07:11 Minimum edge and indentation distance, and sample thickness 08:54 Advantages and disadvantages (Comparison: Brinell, Vickers and Rockwell)