Originally Posted by
Lonewolf_50
riff, are you referring to isotropic superfinishing for gears in the transmissions?
ISF of all gear and bearing hydrodynamic contact surfaces is great way to improve performance under marginal lubrication conditions. It adds some cost but otherwise should have minimal impact on the existing design. Here's an
article on the subject. This is a quote from the third paragraph: "
The results of the current testing reveals that isotropic superfinished SAE9310 specimens show at least a 40°F higher lubricant temperature at the point of scuffing compared to as-ground baseline gears. Based on these results and the previous studies, it was concluded that this isotropic superfinishing technology should be incorporated in all future aerospace gear designs."
In my post I also mentioned recently developed materials that provide significantly increased high temperature capability. In particular there is
C64 steel alloy (AMS 6509) for carburized gears. Since the early 80's X-53 steel alloy (AMS 6308) was the best available material for carburized gears in terms of high-temp capability, with a tempering limit of ~400degF. In comparison, C64 steel alloy has a tempering limit of ~925degF. The tempering temperature of a steel alloy is important because if it is exceeded in service the material will begin to de-temper and lose strength. For rolling element bearings, there is M50NiL (AMS 6278) which is a carburizing grade alloy that can replace the existing standard high-temp material M50 (AMS 6491), which is a through hardening alloy. While M50NiL has similar high-temp capability as M50, it also provides better fracture toughness and lower friction characteristics at boundary contact conditions. Once again, minimizing friction under marginal lubrication conditions is critical for keeping component temperatures down.
To minimize friction in rolling element bearings under marginal lubrication conditions, a recent development is
applying amorphous carbon coatings (DLC) to the rollers/balls. This adds some cost, but otherwise should have minimal impact on an existing design. The only potential issue is how to detect debris generated by this coating.