Since I'm in the technical mood, how about the discussion of different processes applicable to an automotive engine?
I can think of two different fields here, temperature treatments and frictional treatments.
As far as chemical/temperature treatments, I've done some research on cryotreating and nitriding, and have found contradicting information (any metalurgists in the house?).
As I see it, cryotreating is performed by freezing the metal in extreme temperatures.
The way I see it, this would cause impurity atoms within the metal to cluster, and hinder movement of dislocations. However, I've also read that this would cause carbon (impurity) atoms to migrate towards the surface, creating an almost ceramic-quality layer. This would increase the yield strength on the surface (good wear resistance), but maintain a fairly ductile core (if something goes wrong, it probably won't snap, saving a rod or two, and possibly the block).
However, I've also read that it 'repairs' atomic bonds to that of the original metal, yet some say that it's useless for a piece that's already been heat-cycled.
There also seems to be a lot of people that regard it as nowhere near cost-effective.
And some say that it's only worth it for parts such as valve springs, which need fatigue resistance with ductility.
Regarding nitriding, it seems accepted that it is merely a surface treatment. It involves the diffusion of nitrogen into the metal surface. This would obviously require
heating the metal instead of cooling it as in cryotreating in order to permit diffusion. It is supposed to increase fatigue strength. I also saw somewhere that it helps prevent corrosion.
Some people suggest doing both. If so, would it matter what order? One nitriding site says it should be performed last, and another says the metal must be straightened afterwards. Would there be any possible reaction with the carbon and nitrogen built up around the surface together?
Now, frictional treatments. I'm thinking of the obvious shot-peening, as well as polishing (or micro-polishing, as in crankshaft journals, not sure how a rod is 'polished').
Shot-peening consists of tiny beads being shot at high velocities and varying angles into the metal. This would make the tiniest deformations in the metal, probably similar to cold-working steel, increasing dislocation density within the metal. A surface treatment once again increasing fatigue strength.
Micropolishing would create a smoother surface for the bearing to contact, decreasing frictional forces, and increasing bearing life.
Any thoughts? I'm mainly looking at what should be combined with what, and in what order? Also looking for any more in-depth looks at the processes, as well as any others that may be out there.
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i've heard of nitriding, but only in two stroke, or four storke motors........ not too much for cars.......
wait for it... wait for it... NOW GO!! ---> '02 LS Sport <---
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