When specifying DLC coatings for molds, the first mistake I see is treating the quote sheet as the decision document. DLC is not a single material — it spans hydrogenated a-C:H grades, non-hydrogenated ta-C, and doped variants such as W-DLC or Si-DLC, with hardness ranging roughly from 1,500 to 4,000 HV and friction coefficients from 0.05 to 0.2 depending on deposition route (PECVD, sputtering, or arc). For a glass-filled PA66 injection mold running abrasive filler at the gate area, a thin 2–3 µm ta-C layer may outperform a thicker soft a-C:H film; for aluminum die casting or cold stamping of stainless, adhesion and thermal stability matter more than raw hardness. Match the coating grade to the actual wear mechanism — abrasion, adhesion/galling, or corrosion — before you compare prices.
Vendor capability deserves as much scrutiny as the coating spec. Ask for substrate pretreatment details (ion etching depth, interlayer chemistry such as Cr/CrN or Ti/TiN adhesion layers), deposition temperature relative to your mold steel temper — H13 tempered at 540–580°C cannot tolerate processes above that without losing hardness — and achievable uniformity on complex geometry. Coating thickness tolerance of ±0.5 µm sounds tight until you realize a 1 µm overshoot on a core pin changes fit clearance. Request test coupons or a trial run on one cavity insert, measure actual film thickness by calotest, and check adhesion via Rockwell C indentation (HF1–HF4 rating). A supplier who cannot document these numbers is selling hope, not a process.
Finally, build the life-cycle math into your sourcing decision. A DLC coating that adds 20–30% to insert cost but triples polish-to-polish intervals on a high-volume mold pays back within the first production run. Track coating performance per mold — cycles between re-polishing, defect rates at gates and slides — and feed that data back into your vendor scorecard. Coating selection is a life-engineering exercise, not a purchasing line item. For more mold sourcing and supplier evaluation resources, visit MoldSo at www.moldso.com.