Protective Coatings on Steel Dies for Wax Injection Process

Protective coatings are used today in many applications for reducing friction and wear of tools in hot-working process e.g. metal die casting, hot forging, metal die plastics injection. The main goal of undertaken investigation was to evaluate usability of those coatings for improving wear resistance of metal die applied in investment casting process for wax injection. The (Ti,Al)N and (Al,Cr)N PVD coatings were deposited onto X37CrMoV5-1 hot-work tool steel and their mechanical and tribological properties are characterized in the paper. Based on the results of microscope examinations, scratch test, hardness measurement the similar properties of (Ti,Al)N and (Al,Cr)N coatings were found. Moreover it was established that type of steel surface machining before coating deposition, i.e. grinding, electrical discharge machining (EDM) and milling, did not affect coating properties. Thin coatings replicate steel base roughness parameters as Ra, Rz and Rmax with over 95% of correlation. Based on tensile test results of wax/coated steel samples and wax/uncoated steel samples the lowest wax adhesion to (Ti,Al)N coating was confirmed.