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Physical Properties of Steel
Published in Vladimir B. Ginzburg, Metallurgical Design of Flat Rolled Steels, 2020
Knoop hardness test uses a pyramidal diamond indenter that makes a rhombohedral impression with one long and one short diagonal. The loads range from 25 grams to 50 kilograms as shown in Table 3.3. This test is suitable for very small samples of brittle materials. The Knoop hardness number (HK) is given by: HK=14.2PL2Table 3.4 shows the various hardness values for steel that are obtained from several of these different hardness tests [6].
Introduction to Surface Tailoring of Metals
Published in B. Ratna Sunil, Surface Engineering by Friction-Assisted Processes, 2019
In Rockwell hardness testing, a diamond indenter with the round tip as well as a ball indenter (diameter ranging from 1/16″ to ½”) are used depending on the material type. For hard materials, diamond indenter is used, and for soft materials, ball indenters are used. Rockwell method is most reliable and directly gives the hardness value and is widely used in the industry. Testing procedure includes two steps. During measuring the hardness, the workpiece is placed below the indenter, and a preload is applied this is phase I which gives a reference position. In phase II, an additional amount of load is applied known as a major load for a dwell period to allow the elastic recovery. Then the major load is removed, and the final position with respect to the reference point is measured to get the depth of penetration and then converted to a number called Rockwell hardness number. In Knoop hardness test, an indenter similar to Vickers indenter is used which contains non-equal diagonals unlike in the case of Vickers indenter. After the applied load is removed, the major diagonal of the indent is measured, and the Knoop hardness number is calculated. Figure 1.12 (c) shows the diagonal of a Knoop indenter and the corresponding angles of the faces. Usually, for surface hardness measurement, Vickers microhardness, Rockwell and Knoop hardness methods are adopted for measuring surface hardness by considering the fact that the dimensions of the surface coatings and features which generally range in a few micrometers. Brinell hardness is not suitable to measure hardness variation in a range of few hundreds of micrometers and hence not used for surface hardness measurements.
Physical Properties of Metals
Published in Vladimir B. Ginzburg, Steel-Rolling Technology, 1989
Knoop hardness test - This test uses a pyramidal diamond indenter, making a rhombohedral impression with one long and one short diagonal. The loads range from 25g to 50kg. This test is suitable for very small and brittle materials.
Wear-resistant iron-based Mn–Cu–Sn matrix for sintered diamond tools
Published in Powder Metallurgy, 2018
Janusz Stefan Konstanty, Elzbieta Baczek, Andrzej Romanski, Dorota Tyrala
Both grinding and polishing produce a plastically deformed layer. Its depth depends on sharpness and size of the abrasive. Grinding and polishing experiments conducted on annealed brass indicate that the plastically deformed layer extends to 77 and 0.7 μm after plain grinding on #220 SiC paper and fine polishing with 1 μm diamond, respectively, whereas significant plastic deformation occurs only after grinding and extends down to around 8 μm beneath a 2 μm thick heavily scratched skin [6]. Therefore, by using the shallow indentation Knoop hardness test and X-ray diffraction, with the Bragg–Brentano geometry, it was possible to determine the degree of strengthening and to study the phase changes induced by abrasion in the subsurface layer of the metallographic specimens.