Vickers Hardness Testers

The method of hardness measurements on Vickers scales is named after military industrial complex Vickers Limited. The measurements are conducted as follows. An indenter in the form of a four-sided diamond pyramid penetrates into the tested sample under load perpendicularly to the surface. After that the indenter is lifted and the diagonals of the restored indentation are measured with the help of an optical system. Then, using the values of the load and the mean value of the restored indentation diagonal, the hardness value of the sample on Vickers scale is calculated.

Vickers hardness testers are devices that measure hardness according to the stated above method. In standard Vickers hardness testers the applied loads vary from 1 kgf to 100 kgf. Hardness testers with loads from 10 gf up to 50 kgf have gained widespread lately. There exist different mechanisms of load application in Vickers hardness testers. These are: lever-type, stepper motor, direct load. Hardness testers with lever-type loading system have the highest error of load application. These are followed by hardness testers with stepper motor, and the most accurate are Vickers hardness testers with direct load. The quality of the optical system play an important role for the accuracy of measurements on Vickers scales, since the dimensions of indentations vary from 20 to 700 m. As a rule, the optical system of Vickers hardness testers consists of several objective lenses with different magnification. Another source of hardness testers error is the indenter. Since it is technologically impossible to converge all four facets of the indenter, there will always be an intersection at the very top of the indenter. The maximum allowable size of the intersection equals 0,5 m. The angle between the opposite facets should equal (136 0,5) 0.

Vickers hardness testers operate over a broad range. They can measure the hardness of both soft metals (starting from 8 HV) and hard metals (up to 2000 HV). The error of Vickers hardness testers varies from 10% for the load of 10 gf to 2% for the load of 100 kgs. A disadvantage of Vickers method is high sensitivity to the quality of the surface of the tested sample, as well as dependence of hardness on the applied load. As the applied load reduces, the hardness of the sample increases. That is why during hardness control by Vickers hardness testers it is necessary to conduct measurements at strictly corresponding loads registered in technical documents.

See also:

Miniature ultrasonic hardness testers

Rockwell hardness tester -HRC
hardness tester
Brinell hardness tester -HB
-HB / MET-B50
hardness tester
Vickers hardness tester
-HV / MET-V50
hardness tester
Shore hardness tester MET-HSD
hardness tester

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