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Chapter 17: D. Testing Methods 193FIndentationFigure 17.14 Brinell hardness test method.BrinellThis type of hardness test is based on applying forces on an object using a steelor carbide ball with a 10 mm diameter and subjected to a load of 6614 pounds,which can be reduced for softer material to avoid excessive indentation (see Figure17.14). The diameter of the indentation is measured after a certain amount of timeusing a low power microscope, and then the Brinell harness number is calculatedby dividing the load applied by the surface area of the indentation.“Compared to the other hardness test methods, the Brinell ball makes thedeepest and widest indentation, so the test averages the hardness over a wideramount of material, which will more accurately account for multiple grain structuresand any irregularities in the uniformity of the material” (Surface EngineeringForum 2008).Part III.D.4RockwellThe Rockwell hardness test method is also based on applying force on an object tocreate an indentation but using a diamond cone or hardened steel ball indenter. Apreliminary force will be applied on the indenter to be forced into the test materialunder minor load. When equilibrium has been reached an additional major load isapplied with resulting increase in penetration. When equilibrium has again beenreached, the additional major load is removed leaving the preliminary load as is.The removal of the additional major load will allow a partial recovery. The indentationfrom that load is measured and is used to calculate the Rockwell hardnessnumber.Advantages of the Rockwell hardness method include the direct Rockwellhardness number readout and rapid testing time. Disadvantages include manyarbitrary nonrelated scales and possible effects from the sample object support

194 Part III: Inspection and TestApply preliminaryforce F 1F 1 F 2F 1a.Apply additionalforce F 2F 1F 2Part III.D.4Remove additionalforce and measurethe indentationb.c.Figure 17.15 Rockwell hardness test method.Vickersiron blocks. The Vickers and Brinell methods don’t suffer from this effect (SurfaceEngineering Forum 2008).The Vickers hardness test was developed as an alternative method to measure thehardness of materials. This method doesn’t have the arbitrary nonrelated scalesof the Rockwell method and is often easier to use than other hardness tests. TheVickers test can be used for all metals and also can be used on ceramic materials.It has one of the widest scales among hardness tests. The unit of hardness givenby the test is known as the Vickers pyramid number (HV). The hardness numberis determined by the load over the surface area of the indentation and not the

194 Part III: Inspection and Test

Apply preliminary

force F 1

F 1 F 2

F 1

a.

Apply additional

force F 2

F 1

F 2

Part III.D.4

Remove additional

force and measure

the indentation

b.

c.

Figure 17.15 Rockwell hardness test method.

Vickers

iron blocks. The Vickers and Brinell methods don’t suffer from this effect (Surface

Engineering Forum 2008).

The Vickers hardness test was developed as an alternative method to measure the

hardness of materials. This method doesn’t have the arbitrary nonrelated scales

of the Rockwell method and is often easier to use than other hardness tests. The

Vickers test can be used for all metals and also can be used on ceramic materials.

It has one of the widest scales among hardness tests. The unit of hardness given

by the test is known as the Vickers pyramid number (HV). The hardness number

is determined by the load over the surface area of the indentation and not the

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