Intro
13%
Surface treatment sequencing: nitride, PVD, polish, in what order
The build order that takes an H13 forge die from rough block to coated, polished, ready-to-run, and why getting any step out of sequence is a failure mode rather than a slow ramp to nominal life.
A forge shop pulls an H13 die out of service at hit 480. The cavity surface looks like dry paint on a flexible substrate, with sheets of AlTiN coating lifted off the high-pressure zones. The vendor's certificate says the coating was deposited to 4 µm at 450°C, adhesion tested at 65 N scratch load, and shipped clean. The die was vacuum-hardened to 48 HRC, finish-EDM'd to the cavity print, and shipped straight to the coater. Nothing nitrided in between. The coating did its job for 480 hits. The substrate underneath never had a chance to support it.
This lesson covers the build order from rough block to ready-to-run, and the failure mode that hides behind each step taken out of sequence.