Intermetallic formation and its relation to interface mass loss and tribology in die casting dies

摘要

Due to high metal injection velocities typical of die casting process, oxide film on die surface breaks exposing virgin steel surface to liquid aluminum at 680 ℃. This paper describes in detail the fundamental tribochemical basis for the soldering and mass loss phenomena related to this steel-cast metal interaction. Cylindrical plain H13 coupons are dipped in hot liquid aluminum, kept for predetermined times, cleaned and characterized for surface and substrate changes. The thermodynamics behind the formation of intermetallic compounds based on Gibb's free energy calculations are presented. Adhesive strength of soldering layer is determined through pull tests on casting solidified around the test pin. From these results, a dissolution-adhesion wear model is proposed for the growth and dissolution of intermetallics and soldering. In addition, this paper includes the soldering and adhesion behavior of nitrided surfaces. It is seen that the diffusion barrier treatment prevents soldering formation and provides for reduced friction and adhesion at the interface.