I have mud tires and exhaust tips angled behind tires so lot of large rocks hit.
I want my tips black as truck is gray and black so I painted with Bedliner worked great but when tips get hot bedliner bubbles up. I have tried powder coated ones chipped up in few days looking for options

 

High temp paint might work but probably have to be resprayed occasionally.

 

The only way that you're going to prevent nicks and chips from showing is to make them out of some kind of BLACK metal or relocate the tips to where they won't get hit. You're never going to prevent rocks and the like from chipping any kind of coating, not a paint, ceramic, oxide finish or anything else. If you're painting them then you need to use hi temp paint such as that made for BBQ grills. My vote, paint them with BBQ grill paint and touch up as needed.

 

x2. It will be near impossible to keep them in mint condition with 45'd tips. I had them that style on 2 trucks and it just isn't feasible. My last one had the black molded plastic mud flap guards on it and they still got trashed. And I never 'off roaded' it either.

 

Thinking about just cutting them off and putting dumps under their and no having any tips

 

Either take them out the rear under the bumper ..... or repaint front side when you do your wash jobs.
Even on road use will see them pick up dings from kicked up dirt, pea gravels, etc when at 45s. You could get some black chromed ones, but they too will ding.
In time, dumps will accelerate rust behind (and often above) their exits .... exhaust gasses are corrosive as well as moist.