Hardening of internal splines 1

[1MarcoD]

Our company normally specifies splined connections with the splined teeth, both internal and external, surface hardened by either induction hardening to 50-55 HRC (typically on 4140 or 4340 material) or case hardening to 58-63 HRC (8620) or occasionally nitriding. We have a new supplier which says they never harden the internal spline on a flange; in fact they don't normally heat treat flanges at all. Do any of you guys out there think that is unusual? I would be afraid at least of spline fretting, particularly if the external spline was hardened and the internal was not.

Applications are all drivelines (hubs, axles, dropboxes) for heavy military and off-road vehicles, mostly wheeled but some tracked, powered by diesel engine and automatic transmission for the most part. I'd be interested in any comments.

 

[CoryPad]

We have applications that hardened, other applications that are not. Hardened internal splines are more common than not. Your materials and properties are similar to ours. Our applications are passenger vehicle driveline.

 

[CageGear]

Some maufacturers will intentionally leave splines soft on internal couplings. They will act as a fuse in the drive train. They will give or wear faster than the more expensive mating parts.

 

[Dingus187]

I'd agree with cagefear. Mechanical fuse application