Reading wear: crazing, washout, abrasion, adhesive pickup, plastic deformation

Visual: workpiece material smeared back onto the die surface, raised above the die surface rather than cut into it. Under a hand magnifier the smeared material is a different color and finish than the die itself, often shiny where the die surface is matte, and the smear has a leading edge in the direction the billet pulled away. On the matching part, look for craters where material tore out. The two features (raised smear on the die, crater on the part) are a paired diagnostic.

Cause: lube film failure under heat and contact pressure. The billet metal welds to the die metal at the contact moment, and on release the billet pulls away with a chunk of itself stuck to the die, or pulls a chunk of the die with itself. Once material is picked up onto the die, the picked-up material picks up more on the next cycle, and the deposit grows. Adhesive pickup is also the wear mode that distinguishes bare H13 from nitrided H13 most dramatically: bare H13 against hot steel galls aggressively, while a nitrided compound layer with porous graphite-loaded surface resists adhesion almost completely until the case wears through.

On the shop floor: adhesive pickup in a localized region is a lube failure in that region. Adhesive pickup across the working face is a lube failure across the working face, or the case has worn through to bare substrate and the die is at the end of its surface-treated life. Increase lube film thickness, change to a higher-film-strength lube chemistry, or check whether the die has been running hot enough to flash the lube carrier before the parting solid deposits. The pickup is the symptom. The cycle conditions are the cause.