OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 4 2023 Micro-indentation The elastic modulus and microhardness testing was performed on a DUH-211S Dynamic Ultra Microhardness Tester (Shimadzu, Japan) fitted with a Berkovich three-sided pyramid indenter with α = 65.03°. The maximum test force was 2,000 mN (fig. 6). The indentation elastic modulus is calculated from (5), where Poisson’s ratio for diamond is 0.07, the elastic modulus for diamond is 1.14‧106 N/mm2, in this case the reduced elastic modulus in the indentation region Er is determined as follows: , 2 r p S E A π = (15) where Ар is the cross-sectional area of the contact surface between the tip and specimen, which is determined by the load curve on F–h diagram and the tip area function. For the Berkovich tip, Ар is calculated as follows: 4.8 . 96 p c A h = (16) The DUH-211S provides a continuous measurement of the material stiffness along with loading and displacement as a continuous function of the penetration depth. The hardness and elastic modulus are calculated at each data point recorded during testing. Microhardness measurement A DuraScan-10 hardness tester (EMCO-TEST, Austria) for high load range testing was used to measure the hardness under 100 g load for 3 s. Measurement was conducted in the XZ plane, on the left side at point 0 (see fig. 1, b). Fig. 6. General view of a DUH-211S Dynamic Ultra Microhardness Tester (a); test section (b): 1 – probe, 2 – specimen; schematic loading (c): 1 – Berkovich indenter, 2 – specimen; point of indentation (d) b а c d 2 1 20 µm
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