Indenter is a part of great importance in hardness testing. Its accuracy and quality is the important factor to ensure accurate value. Due to different testing methods, the indenter has different materials, geometrical switches and requirement of accuracy.
Sort by materials:steel, carbide alloy, man-made corundum and natural diamond cone.
Sort by shapes: spheroidal, conical, cylinder-shaped, regular pyramid and rhombus cone.
Sort by test methods: φ10、φ5、φ2.5 and φ1 mm carbide alloy indenter for Brinell hardness testing. φ1.588 and φ3.175 mm chilled steel or carbide alloy indenter, or diamond cone indenter with 120° intersection angle for Rockwell hardness testing. Tetrahedron diamond cone indenter with opposite side intersection angle of 136°±0.5°for Vikers hardness testing. Selection of the indenter should be accordance with test methods, hardness tester type and testing objects.
(1) Inspection of Brinell indenter
The new standard stipulates that indenter ball should be made by carbide alloy material instead of steel ball in primary standard. Because the indenter ball is one of the standard instruments in Brinell hardness testing, the tolerance range of indenter ball diameter should be controlled as little as possible, otherwise it will affect the accuracy of Brinell hardness value.
In the GB/T 231.2, the stipulation of Brinell hardness indenter diameter allowable error is shown in the following sheet:
Table 1. Allowable Error of Carbide Alloy Indenter Diameter
(2) Inspection of Rockwell Indenter
In Rockwell hardness testing, two kinds of indenters are applied, they are diamond circular cone indenter and spheroidal indenter.
Table 2. Allowable Error of Rockwell Hardness Indenter