REACTION OF SEVERAL IRON AND NICKEL BASED ALLOYS WITH SINTERED LI2O PELLETS

The reaction of type 316 stainless steel, Incoloy 800, Hastelloy X-R, Inconel 600 and pure Ni with sintered Li2O pellets has been studied between 800 and 1100°C under dynamic vacuum. The reaction products were analyzed by means of metallographic, microprobe and X-ray diffraction methods. The reactions proceeded measurably between 800 and 950°C and appreciably at 1000°C, being greatest with Incoloy 800 and least with Hastelloy X-R. Among the primary alloy constituents, chromium was exclusively attacked by lithium and oxygen diffusing from the Li2O into the alloys to form LiCrO2. This phase grew into a reaction zone (subscale) of uniform thickness beneath the surface of each alloy. Preferential growth of LiCrO2 along the grain boundaries was observed only in the case of Inconel 600 below 950°C. On the other hand, iron diffused toward the Li2O pellets to form volatile Li5FeO4. However, any reaction product associated with Ni was not detected and Ni metal was little attacked by the Li2O pellet over the whole range of reaction temperature. © 1979.