Rockwell Superficial Hardness Test

The Rockwell Superficial hardness test method consists of indenting the test material with a diamond cone (N scale) or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load F0 (Fig. 1A) usually 3 kgf. When equilibrium has been reached, an indicating device that follows the movements of the indenter and so responds to changes in depth of penetration of the indenter is set to a datum position. While the preliminary minor load is still applied an additional major load, is applied with resulting increase in penetration (Fig. 1B). When equilibrium has again been reach, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration (Fig. 1C). The permanent increase in depth of penetration, e, resulting from the application and removal of the additional major load is used to calculate the Rockwell Superficial hardness number.

HR = E - e


F0 = preliminary minor load in kgf
F1 = additional major load in kgf
F = total load in kgf
e = permanent increase in depth of penetration due to major load F1, measured in units of 0.001 mm
E = a constant of 100 units for diamond and ball indenters
HR = Rockwell hardness number
D = diameter of steel ball

Rockwell Superficial hardness test principle
Larger View
Fig. 1 Rockwell Superficial Principle


Rockwell Superficial Hardness Scales
ScaleIndenter TypeMinor Load
F0
kgf
Major Load
F1
kgf
Total Load
F
kgf
Value of
E
HR 15 NN Diamond cone31215100
HR 30 NN Diamond cone32730100
HR 45 NN Diamond cone34245100
HR 15 T1/16" steel ball31215100
HR 30 T1/16" steel ball32730100
HR 45 T1/16" steel ball34245100
HR 15 W1/8" steel ball31215100
HR 30 W1/8" steel ball32730100
HR 45 W1/8" steel ball34245100
HR 15 X1/4" steel ball31215100
HR 30 X1/4" steel ball32730100
HR 45 X1/4" steel ball34245100
HR 15 Y1/2" steel ball31215100
HR 30 Y1/2" steel ball32730100
HR 45 Y 1/2" steel ball34245100


Rockwell superficial scales are used to test materials too thin or small for the regular scales or outside the regular ranges. Generally Diamond Indenters are used for hard materials while Ball Indenters are used on soft materials. The HR 15 N scale is useful for testing hard thermal spray coatings like ceramics and carbides, while at the other extreme the HR 15 Y scale is used to test very soft abradable coatings.





Links To:

Hardness Testing

Rockwell Hardness Test

Rockwell Superficial Hardness Test

Brinell Hardness Test

Vickers Hardness Test

Microhardness Test

Mohs Hardness Test

Scleroscope and other hardness testing methods


Hardness Conversion Tables and Charts:

Hardness Conversion Table(colour version - may take time to load)

Hardness Conversion Table(non-colour version)

Hardness Conversion Chart (1)

Hardness Conversion Chart (2)

Chart of Brinell, Vickers and Ultimate Tensile Strength Equivalents (1)

Chart of Brinell, Vickers andUltimate Tensile Strength Equivalents (2)

Hardness Conversion Table related to Rockwell C Hardness Scale (hard materials) (colour)

Hardness Conversion Table related to Rockwell C Hardness Scale (hard materials) (non-colour)

Hardness Conversion Chart related to Rockwell C Hardness Scales (hard materials)

Estimated Hardness Equivalent Chart related to Rockwell C and Vickers (hard materials)

Hardness Conversion Table related to Rockwell B Hardness Scale (soft metals) (colour)

Hardness Conversion Table related to Rockwell B Hardness Scale (soft metals) (non-colour)

Hardness Conversion Chart related to Rockwell B Hardness Scale (soft metals)

Table of Minimum Test Piece Thickness for Rockwell Hardness Testing using Ball Indenters

Table of Minimum Test Piece Thickness for Rockwell Hardness Testing using Diamond Indenters

HV, MPa and GPa Conversion Calculator

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