reworking fretted/undersize coupling seat on motor shaft

[gneerman]

Machine Description: 1250hp vertical 1200rpm, vertical motor driving a pump through a rigid coupling. Motor shaft extension is 4.375" at the coupling seat. The design hub/shaft fit is 0.000-0.002" clearance. There is also a key approx 1" square, 5" long.

Problem: During refurbishment, the motor shaft was found undersized and fretted at the location where the coupling seats.

Options under consideration:

1. machine it down and bore a new coupling hub to match the shaft. However that is suboptimal because parts would no longer be interchangeable among sister motors.
   OR
2. machine down, build up with chrome or weld, machine to final dimension.

Are there any downsides to option 2? I'm aware that it's a standard repair for bearing seats, and just wanted to check if it is also acceptable for coupling hub seats.

(Asking for a friend)

 

[Artisi]

I don't see a problem with either, plus I don't see any problem with option 1 of the interchangeability, if the case ever arose take the coupling with the motor.

 

[JJPellin]

I have seen Chrome plating crack or delaminate. Welding stresses can result in runout or cracks (depending on the shaft material). I agree with Artisi. I would clean up the shaft and make a new hub. Do you know the reason for the fretting? Poor alignment. Excess runout. Frequent start/stop cycles. Highly corrosive environment. Poor fit from original installation. Bad maintenance practices such as excessive polishing with emery cloth during routine repairs.