Mht 10 microhardness tester

Microstructural characterization of the tensile specimens was performed by optical microscopy using Leica DMI 5000 M and by SEM. A horizontal and a vertical plane from a Z tensile specimen were polished on a Struers TegraPol-35. The samples were polished with a final sand paper grit size of 1200 grit and subsequently with diamond suspension from 6 µm to 1 µm sizes. The microsections were then etched with a Ti ASTM 186 chemical agent for 30 s.
The Vickers Hardness (HV) was measured on the microsections of tensile specimens produced with both powder batches, on one horizontal (X orientation) sample per batch and one vertical (Z orientation) sample per batch, i.e., on a total of four samples. HV was measured using an MHT-10 Microhardness tester (Anton Paar GmbH, Graz, Austria), using a load of 200 gf with a 30 s hold time, and measuring with a 50× optical magnification.

A Knoop diamond under a load of 50 g and a dwell time of 10 s was used to perform six different indentations at 25 μm intervals (MHT-10 Microhardness Tester; Anton Paar, Graz, Austria). The lengths of the long axes of the indentations were measured using an optical analysis system (Leica DMR Microscope; Leica Mikroskopie und Systeme, Wetzlar, Germany) and used to calculate the SMH (the average value from the six indentations). This procedure was performed before the first erosion (initial SMH) and after each erosive cycle. Relative SMH (rSMH) at time t was calculated using the formula rSMH = (SMH_t/SMH_i * 100), where SMH_i is the initial SMH before any erosive challenge and SMH_t is the value at time t.
The lengths (L) of the long axes of the indentations were further used to calculate the depths (D) of the indentations according to the formula D = L/2 * tan α, where α = 3.75 deg, a known parameter of the Knoop diamond indenter.