DLC coating for splines

[milq]

I was just wondering if anyone has ever tried having a DLC or similar type coating applied to new splines. The thickness of such coatings is usually around 4 microns thick so I'd think it shouldn't affect fit of the units as that's well below manufacturing tolerances. The hardness is typically approaching 80+ Rockwell C, which is very hard. There are tons of different options out there, some with added lubricity as well. Just thinking out loud a bit.

Any coatings folks on here?

[natalena]

The coating is still bonded to a soft substrate that is susceptible to deforming under load. The coating would probably retain the characteristics, albeit chip or fracture with the spline original metal movement underneath. Sort of like seeing people pour 4" depth concrete driveways on sand base, and wondering why it breaks up in a couple years. Keep thinking though, a permanent spline solution has to be out there :)

[milq]

Yeah, I had also wondered about induction hardening as it tends to be deeper, although it's still considered a surface treatment. Wish I knew more about the metallurgy in the pinion shaft in particular. If anyone has a trashed pinion with at least some of the original spline left, I've got a Rockwell hardness tester and I'd pay the shipping costs (both ways if you wanted it back).

[Martin]

Depending on what you want to wear, hardening the drive shaft splines would make for more wear on pinion shaft. Hardening the pinion shaft would mean more wear on the pinion shaft. Unsure what will wear if you do both.
Regards Martin.