303 stainless steel to brass galling

I am designing a small rotating shaft made of 303 stainless steel with a max RPM of 12,000 rpm then decelerating to 0 rpm in approximately 2 seconds. The shaft is .1179 in diameter with a SR .125 on the end contacting a flat .032 thick hard brass disc. The axial loads are light however they are enough that over time a small spherical impression is made in the brass disc. I believe this "impression" does not continue to deepen due to work hardening of the brass over time. My question is this: some of the test personnel have observed unusual wear patterns in the brass they claim to be galling. I do not believe galling is the issue since the 303 stainless and hard brass do not have a galling issue when used together. If I am incorrect in my belief what type of material should the disc be made of or should the disc be plated with nickel or chrome?

Yes galling can occur with the 3 series s.s. . A light nickel plating would take care of that problem.