No that would not be "normal". Have you ever pulled this trailer before? Is this a new ball, or first time you pulled with it? If you did start with a clean and lubed ball, then the ball if self is of poor quality (cheap) or there was something wrong with the coupler. Which ever it is, now you have to fix it. The ball is useless so you might as well toss it, and get a "good" replacement. The coupling if not to bad can be cleaned up with a die grinder and some patients, if you can get it smoothed out, take it to someone who can, or replace it. Most of these couplers are welded on so that will take some work. After everything is fixed, use only EXTREME PRESSURE GREASE this is made for applications like hitches, wear balls see very high loads. Good luck.