Tantalum Diffusion Layer for Extremely Corrosive Environments

Ultramet has been developing and commercializing refractory metal and ceramic coatings and freestanding parts for corrosive and high temperature environments for more than 44 years. Under NASA funding, Ultramet developed a process to diffuse highly corrosion-resistant tantalum metal into the surface of conventional stainless steels and superalloys to improve the acid corrosion resistance of components used in precision propellant transfer valves on the space shuttle. A thin, metallurgically bonded tantalum surface layer was established that graded from pure tantalum at the surface to a mixture of tantalum and the substrate elements. The tantalum surface layer precisely replicates intricate substrate features and for some applications does not require post-process machining or polishing. Additionally the tantalum surface technology has been applied to industrial applications such as heat exchangers, rupture disks, instrumentation, pumps, valves, fittings, and custom equipment. Ultramet’s application experience and the performance of tantalum diffusion coatings will be reviewed.