The Vickers hardness test method was proposed by R.L.Smith and G.E.Sandland in 1921. The British company Vickers-Armstrong (Vickers-Armstrong) trial-produced the first hardness tester tested in this way. The Vickers hardness tester is a high-tech product of opto-mechanical and electrical integration. The machine is novel in shape, has good reliability and operability. It is a new type of Vickers and Knoop hardness tester using precision mechanical technology and photoelectric technology.
The Vickers hardness tester has many test forces. As long as the surface roughness of the workpiece meets the standard, the Vickers hardness tester can detect it. The Vickers hardness tester uses a stepping motor to press on the surface of the workpiece, and then a reading microscope measures the length of the diagonal of the indentation. Then, the Vickers hardness is measured by using a conversion relationship between the diagonal line and the test force. In addition, the Vickers hardness tester measurement software can be installed, and the image can be displayed on the computer screen, which makes the operation and measurement of the hardness value more convenient and faster.
With a load of 49.03～980.7N, the Vickers hardness tester presses the surface of the material with a square cone diamond indenter with an angle of 136° on the opposite surface. After holding it for a specified period of time, measure the diagonal length of the indentation, and then press the formula. Calculate the size of the hardness. It is suitable for the hardness measurement of larger workpieces and deeper surface layers. Vickers hardness still has a small load Vickers hardness, test load <1.949.03N, which is suitable for the hardness measurement of thin workpieces, tool surfaces or coatings; micro Vickers hardness, test load <1.961N, suitable for metal foil, Hardness measurement of very thin surface layer.
The test force divided by the surface area of the indentation is the Vickers hardness value. Vickers hardness value calculation formula: HV = constant × test force/indentation surface area ≈ 0.1891 F/d2 ………… Where: HV ――― Vickers hardness symbol; F ――― test force (unit N); d ――― The arithmetic average of the two diagonals d1 and d2 of the indentation (unit: mm). In practice, the Vickers hardness value can be obtained by looking up the table according to the diagonal length d. The national standard stipulates that the diagonal length of Vickers hardness indentation ranges from 0.020 to 1.400mm. See the above diagram of the Vickers hardness tester principle.