question about inflation for impeller

sandy

hello all, I am trying to apply inflation on an impeller to get smaller y+ on the walls. Here is my problem. 1) when I apply inflation only on the blades, I can see the prism clearly. 2) when I apply inflation only on shroud and hub, it also works perfectly. But, 3) when I apply inflation on all the blade, shroud and hub, I can not see any prism at all.

Any one could please tell me how to do it? Thanks in advance.