I've had the same problem with my mokume(quarters) and pattern welded steel. Which is, when forging the face everything goes great. When forging on the edge(hammering on the visible stacked layers) my billet begins delaminating very quickly. Everything looks good, check the edge on the grinder, then it splits. Just to save you all some time, I understand the science but my skills and equipment is where I'm short. Also, the mokume was hot when it split but not hot enough to crumble, the layers were solid when cold.
Any tips or ideas are appreciated.