Alexander,
Mixing media of different types or hardness is generally not a good idea. Are you concerned about ferrous contamination on the parts that are peened with ceramic shot, or are you just concerned about cross contamination of media types? I can tell you that we have machines that are capable of running two sizes of media, but we would never have two different types, the only difference we allow is size, i.e. ASH-70 and ASH-170.
How close in size is the cast steel/CCW to the ceramic bead you are using?
