Improving H13 steel mold life applying surface coatings for AlSi12Cu4Ni2Mg cast alloy

This study evaluated the performance improvement of different surface coatings applied to increase the life of an AISI H13 steel permanent mold for casting AlSi12Cu4Ni2Mg alloy. To reach this goal, the coating adopted should be resistant to wear and to the welding process, which occurs through iron diffusion from the H13 steel mold to the cast Al alloy. The following surface coatings were applied to H13 pins and tested: Nitrocarburizing, Duplex (plasma nitriding with multilayered CrAlN/CrTiN-based cathodic arc deposition), and Boronizing. To evaluate surface degradation, one specimen for each coating was tested in different conditions: pins before service and pins after 40,000 production cycles. The specimens were characterized by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), and mechanically by Vickers microhardness test. In conclusion, the duplex CrAlN/CrTiN-based coating deposited by a cathodic arc on a nitrided AISI H13 steel pin increased the mold service life within a 24 % minimum compared with that of the nitrocarburizing coating, which was the standard coating until present. The boronizing coating showed acceptable performance, but adjustments in the production process are needed to increase the service life of the H13 mold. This work confirms how a technical and daily industrial steel mold material can be improved applying a materials science and engineering scientific routine, within microstructure characterization tools to improve performance and production in an Al cast part plant.