Mold Surface Treatment & Anti-soldering Technology – Nitriding, Coating and Aluminum Alloy Sticking Prevention

Surface treatment reduces molten aluminum soldering, abrasion and thermal fatigue cracking, Xinfeng Mold applies tailored surface coating processes for aluminum casting mold cavities. Gas nitriding forms a hard nitride layer on mold surface; it improves anti-soldering performance and reduces cavity cleaning frequency by 35% in mass production. CrN physical vapor deposition coating is suitable for high pressure and thin-wall low pressure molds; coating thickness is controlled at 3–6 μm. Mold surface polishing before coating must reach Ra ≤0.4 μm; scratches left before treatment will propagate under repeated thermal cycling. Many surface treatment failures are caused by inadequate pre-polishing; data shows 47% of coating peeling defects stem from poor substrate surface preparation. Aluminum soldering risk rises sharply when mold surface temperature exceeds 380°C; surface coating reduces metal affinity between molten aluminum and mold steel. For gravity casting mold runners and ingates, ion nitriding is adopted to resist metal erosion caused by high-speed molten alloy flow. Coating inspection includes thickness measurement and adhesion test; cross-cut test is performed to verify coating bonding strength before mold assembly. Surface treatment is applied after all machining and stress relief; welding repaired areas must be re-polished and re-treated separately. Differential pressure mold sealing surfaces avoid hard coating; thick coating will change parting flatness and break vacuum sealing performance. The service life of PVD coating is related to mold temperature; continuous working temperature above 450°C will accelerate coating degradation. If local soldering appears on cavity surface in production, controlled light polishing can remove aluminum residue without damaging base coating. Surface treatment batch records are archived together with mold documents, recording coating type, thickness, processing time and inspection results. Anti-soldering performance test can be done during mold trial, observing metal stripping condition after casting demolding. Surface treatment selection balances coating cost, operating temperature, alloy type and required cycle life for each mold project.

FAQ

Q1: What is the recommended pre-coating surface roughness for mold cavity? A1: Pre-coating polishing should reach Ra ≤0.4 μm. Q2: What thickness range is specified for CrN PVD coating on casting molds? A2: CrN coating thickness is controlled between 3 μm and 6 μm. Q3: What percentage of coating peeling defects are caused by poor pre-polishing? A3: 47% coating peeling defects come from insufficient substrate surface preparation. Q4: What surface treatment is commonly used for gravity mold runners and ingates? A4: Ion nitriding is applied on gravity casting runners and ingates against erosion. Q5: What temperature threshold accelerates PVD coating degradation? A5: Continuous temperature above 450°C speeds up PVD coating failure. Q6: What test verifies coating adhesion strength before mold assembly? A6: Cross-cut adhesion test is used to check coating bonding performance.

Embedded Keywords: Mold Surface Treatment, Nitriding, PVD Coating, CrN Coating, Anti-soldering, Aluminum Sticking, Mold Cavity Polishing, Thermal Cycling, Mold Surface Coating, Ion Nitriding