Somewhat similar to Vickers, it employs an elongated diamond pyramid, test forces usually not exceeding 1 kgf, and a precision microscope or high-resolution USB camera.

The Knoop indentation test is used to measure a material’s relative microhardness via the depth its indenter penetrates. The machine is typically a floor model and more expensive than Brinell and Rockwell units. Vickers hardness tests deliver extremely accurate readings and require only one type of indenter. For testing where 1 kgf or less is needed, a micro-Vickersunit can be employed along with a precision microscope or high-resolution USB camera in order to visualize and measure indentations using magnifications up to 600x typically (up to 1,000x increasingly). The indenter is an upside-down pyramid shape with a square base and an angle of 136 degrees between opposite faces. Vickers adds a microscope or USB camera to visualize and measure the indentation caused on a test sample, especially those with extremely hard surfaces, by a diamond indenter (Fig. Here are Rockwell test samples broken down by HR scale: A (cemented carbides, thin steel, shallow case-hardened steel) B (copper alloys, soft steels, aluminum alloys, malleable iron) C (steel, hard cast irons, pearlitic malleable iron, titanium, deep case-hardened steel, plus other materials harder than B) D (thin steel and medium case-hardened steel, pearlitic malleable iron) E (cast iron, aluminum, magnesium alloys, bearing metals) F (annealed copper alloys, thin or soft sheet metals) G (phosphor bronze, beryllium copper, malleable irons) H (aluminum, zinc, lead) and K, L, M, P, R, S and V (bearing metals, plus other very soft or thin materials). If you are working with brittle or very thin materials (e.g., thin strip or lightly carburized surfaces, small parts or parts that might not hold up under a standard Rockwell test), then Superficial Rockwell scales should be used for lower force and shallower impressions, specifically a 3 kgf preload and main test force of 15, 30 or 45 kgf. Depth of the impression is measured (Fig. Rockwell indents the test material with either a diamond core (HRC) or a hardened (tungsten) steel-ball indenter (HRB, etc.) by applying a preload of 10 kgf followed by a main test force of 60, 100 or 150 kgf.

Whether you do Rockwell or Superficial Rockwell will depend on the material you are testing. Here is a rundown of hardness tests to help you determine which are best suited to your operation. These scientists recognize a number of common tests, including Rockwell, Vickers, Knoop and Brinell, but even these are further segmented by Rockwell Superficial and micro-Vickers.

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