Niobium-based Alloy

C-103 is a niobium alloy containing 89% niobium, 10% hafnium, and 1% titanium that is used in liquid rocket booster nozzles, such as the main engine of the Apollo lunar module. The Apollo Service Module used another niobium alloy. Because niobium begins to oxidize above 400°C, a protective coating is applied to its surface to prevent it from becoming brittle.