ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2025 32 drive. There are options to apply the weight load such as on digital systems that use weights to apply the load or use a closed loop load cell to apply the weight load (Fig. 3). The latter affords greater precision and repeatability. With a weight-loaded system, the level of the machine is of great importance, can be used to directly measure in the most popular regular Rockwell hardness scales and can quickly convert that hardness value into HB (Brinell), HV (Vickers), HK (Knoop) and many other scales. Other features include the ability to obtain ultra precise results, a wide measuring range, and scale/ selectable test force capabilities. Also, automatic main test force loading/ unloading, a high-resolution digital display, and USB data storage are all very advantageous (Fig. 2). A user-friendly touchscreen interface speeds operation and data can be transmitted via USB output to a flash TABLE 1 — HARDNESS TESTING METHODS COMPARISON Hardness scale/method Suitable materials Advantages Limitations Applications Load range Indentation type Standards Rockwell C, HRC Metals, alloys Quick, easy to use, widely recognized Limited precision on soft, thin materials Quality control, bulk material testing 150 kgf 120° diamond spherical ASTM E18, ISO 6508, DIN 50103 Rockwell B, HRB Softer metals, aluminum alloys, non-hardened steels Suitable for softer materials, fast Limited for very hard materials Quality control, non-hardened metals 100 kgf Spherical (steel/ tungsten ball) ASTM E18, ISO 6508 Brinell Metals (e.g., steel, aluminum), castings Large indenter for average hardness Not suitable for very hard materials, large indentations Large parts, castings, forgings 62.5-3000 kgf, 62.5-1000 kgf (for aluminum) Spherical (steel/ tungsten ball) ASTM E10, ISO 6506 Vickers All materials especially thin sections and coatings High precision, small indentation Slower process, more expensive equipment Microhardness, thin films, small parts 10 g-1 kg Diamond pyramid ASTM E92/ E384, ISO 6507 Knoop Brittle materials, ceramics, thin coatings Ideal for very small or thin samples, anisotropic materials Complex to perform, not suitable for bulk properties Ceramics, glass, coatings, small samples 10-1000 gf Asymmetrical pyramid ASTM E92/ E384, ISO 4545 Leeb (rebound) Metals, large parts Portable, suitable for large parts Lower precision, sensitive to surface conditions Onsite testing of large parts, rough surfaces N/A Rebound ASTM A956, ISO 16859 Ultrasonic Metals; small, thin, and large parts Portable, fast test, nondestructive, both small and large parts Sensitive to operator application of load All metals 0.3-10 kg 136° diamond pyramid ASTM 1038
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