36
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January - February 2015
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www.machinerylubrication.com
IN THE TRENCHES
WE S CA SH
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NORI A CORPOR AT ION
t has been proven that the No. 1 cause of machine failure is
the degradation of component surfaces. These surfaces can
degrade in a variety of ways, but the most destructive is via
particle contamination. While you may already be aware that dirt is
harder than most metals found in machines, do you know how
much harder it is?
Before analyzing the differences in the hardness of materials,
you must fi rst understand how hardness is measured. A quick
Internet search for hardness measurements likely would yield three
general methods: Rockwell hardness, Vickers hardness and Mohs
hardness. Although each of these tests is a little different, they all
measure a material's strength by indenting or scratching.
Rockwell Hardness
The Rockwell hardness test method has several scales that are
based on the tester's indenting tip. However, they all work similarly.
A load is applied to the indenter, which then transfers the load to
the material being tested. At the conclusion of the test, the inden-
C o n t a m i n a t i o n C o n t r o l
The HARD TRUTH About
Particle
CONTAMINATION
I
500
mg/L
Iron
Dust
(5
Mohs
Hardness)
500
mg/L
Bearing
Metal
Particles
(6-7
Mohs
Hardness)
500
mg/L
Silica
Dust
(7-8
Mohs
Hardness)
500
mg/L
Diamond
Dust
(10
Mohs
Hardness)
25 mg
Wear Debris
120 mg
Wear Debris
170 mg
Wear Debris
>1,000 mg
Wear Debris
Particles of high compressive strength (hardness) and angularity (sharp edges) cause the greatest damage.
