Posted by Dan Shockley on Friday, January 19, 2001 at 11:28AM :
In Reply to: Nitriding my crankshaft posted by Matt Wilson on Thursday, January 18, 2001 at 10:46PM :
There are several process that are being confused here. First of all TiN is a coating that is applied at a low temperature. It is just that, a thin coating that protects the metal underneath. This would be catostrophic to a crank shaft. The coating is an intermetallic. This means that it is brittle and hard. It would chip off and destroy the bearings.
The other two processes are Caborizing and nitriding. For these two processes the part is heated in an atmosphere of either Nitrogen or Carbon Monoxide. At elevated temperature the diffusion rate of the C/N in to the part is faster. These heat treatment processes affects the composition of the outer layers of the part. The treatment depth is determined by the time and the change in composition of the base metal is dependant on Carbon / Nitrogen potential. The result is a part with a soft pliable center and a hard "tough" outside. This is commonly done on parts like crank shafts and axle shafts. If the outer layer becomes too thick fatigue failure will occur. This could be possible if you try to "re-treat" your crank shaft. With out sectioning the crank and examining the effects of prior heat-treatment I would not recommend this(of'course this would destroy the crank) .
Carbo-nitriding is just the combination of the two processes.
I hope this helps clear up some confusion,
ferrously yours,
Dan
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