On Thu, 22 Sep 1994, Harry Phinney wrote:
> Not all steels
> respond well to nitriding, and while I would expect that most steels
> used in crankshafts would benefit, they will not all benefit equally. I
> doubt that it would be appropriate for use on nodular iron cranks, but
> I'm not certain.
In fact some alloys of steel are actually weakened by Nitriding. I don't
remember the details, but if I remember correctly it has to do with the
skin tension created by the process, which can cause surface cracks in
alloys incompatible with Nitriding. I'm pretty sure you can't Nitride
noduar iron cranks.
> There are some other treatments which I have heard of, but am not
> familiar with. One which comes to mind is called "Tuftriding", and was
> used on some BL cranks. I believe this process works well on at least
> some steels which do not respond particularly well to nitriding.
Tufftriding produces a thinner hardened layer than Nitriding, but can be
used on a wider variety of materials (including nodular iron, I
believe). It's the hardening process of choice for original XPAG/XPEG
cranks (MG T-Series), which are a steel alloy that can't be Nitrided.
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Chip Old 1948 M.G. TC TC6710 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO (daily transportation)
feold@umd5.umd.edu
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