Nickel Plated Invar-36 Alloy for Carbon Fiber Composite Molding Tools

摘要

Invar tooling has been increasingly used for low volume molding of precision carbon fiber composite parts with complex geometry. To expand its applications to high volume production, this study examined the feasibility of hardening Invar-36 alloy with a thin layer of electroless nickel for surface durability improvement. Two commercial coatings were subjected to thermal cycling tests and evaluated for their changes in hardness, surface roughness, surface morphology, and coating-substrate interface. The results indicated that both coatings can withstand the heating/cooling cycles experienced by production molding cycles, but one was considerably harder than the other. With a 70 μm thick nickel surface layer, Invar samples plated with the harder coating had an HRC hardness of 50, comparable to the P20 tool steel commonly used for automotive composite molding. The surfaces were not exposed to combined molding and thermal cycling in this study. Nonetheless, the results support the choice of this electroless nickel coating for the targeted application.