What kind of metallizing system did you use? Powder metal or atomizing wire?
That is definitely a bit on the heavy side for powder application, because I think the powder skin gets overheated relative to the parent metal, and thermal contraction later causes delaminating of the spray. Bear in mind that the powder is not fused to the surface, so it does not take much to dislodge it. Dull tools/loaded wheels will also break it loose due to inelastic local compression/decompression under the contact point.
How do you guys typically perform the surface prep? Contamination was always a concern, even the preheat oxidation layer was suspect to me. I'd preheat then rough turn then use the bond coat immediately, however I never tackled anything nearly as big as what you have there. I'll bet you've got a few $$ tied up in materials on that one