Experimental Evaluation of Ceramic Coatings for Die Protection in Low-Pressure Die-Casting Process

One of the most important factors in the LPDC process is the heat transfer during the solidification of the molten alloys, which is responsible for the resulting microstructure and, thus, the quality of the cast piece. The use of foundry coatings has been lately suggested as a proper strategy to control the heat transfer while protecting bonded moulds from aluminium adhesion by providing a barrier between the surface and the liquid metal. LPDC die coating failures usually come from the loss of adherence or excessive wear originated in the successive filling processes, which requires stopping production for the reapplication of the coating. In the present work, coatings with different insulation capabilities have been evaluated, in terms of adherence and wear tests, in order to select the most promising alternative for LPDC die coating. This study confirmed that surface preparation and cleanliness are vital for an adequate adhesion of the coatings to ensure their durability. The results evinced that the use of a primer layer provided a higher adhesion of the coatings and considerably improved their perfomance. The coating that presented the best results in terms of adhesion and wear resistance under different abrasive testing conditions was coating B3.