<VV> Re Nitriding was Oil Pump

[Stan East]

------------original message------------
From: "Ron Guy" <qcc65@charter.net>

<snip>
If Nitriding is surface treating then a 10/10 turned crank no longer has any
benefit from nitriding.
Is this sound thinking or is it more complicated than that?

Ron Guy
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This is an answer I gave 18 months ago about nitriding....

 Answer...
Nitriding consists of subjecting the heat treated article (crankshaft) to
the action of ammonia gas at temperatures from 930 deg F to 1200 deg F for
long periods of time. One of the major factors in the nitriding of steel is
the presence of alloying elements such as chromium, aluminum, vanadium, and
molybdenum in the steel. These elements are included because of their
tendency to produce nitrides. Nitrides are hard grains within the steel. A
wide variety of alloy structural steels and tool steels are nitrited to
extend service life.

The nitriding process achieves a high surface hardness while maintaining the
toughness of the parent metal. This is achieved because the nitriding is
only a shallow depth into the surface of the part rather than through the
entire thickness. The nitriding process also achieves some surface stress
reduction from the previous finishing process. The depth of nitriding can
vary depending on application and process time from .008" to .030" deep.

A nitrided crank should wear more slowly and have a longer fatigue life
(number of cycles before failure). Nitrided cranks are used in higher
performance applications and see higher loads and faster cyclic loading than
a lower performance application crankshaft might see, however the lower
performance crankshaft in the same high performance application would often
fail prematurely.

Additional comments this time...

Yes if the nitriding is .010" or less the ground down crank will no longer
be nitrided in the journal area. It depends on the depth of nitriding and
it's not easy to measure. The best method to measure nitride depth is by
destructive cutting and expensive electron microscopes, of the part, (not a
good idea). However a good grinder will know that he has gone through the
nitriding while grinding the effort to grind will change very fast.

Stan East

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