The reaction between liquid zirconium and graphite at temperatures above 2000 C has been investigated. The reaction products were found to be carbon saturated zirconium metal and ZrC which formed between the graphite and the metal. Parabolic growth behavior was observed for the ZrC phase at all temperatures of this investigation. The parabolic growth constant at temperatures between 2000 and 2860 C was measured 2 to be 1.83 exp (-84,300/RT) cm /sec. The reaction mechanism was proposed to be the rapid carbon saturation of the liquid metal and the formation of ZrC at the metal-carbide interface with diffusion of carbon through the ZrC the "rate determining step" of the reaction. The concentration independent diffusion coefficient of carbon in ZrC, (D), was proposed to be 0. 95 exp (-78, 700/RT) cm /sec. This value was calculated using the temperature invariant ZrC phase fields proposed in the literature. The Zr(liq)l-Zr(liq) + ZrC I phase boundary over the temperature range 2000 to 2800 C was determined. The ZrC + C eutectic temperature was found to be 2890 + 50 C.

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Direct reaction of liquid vanadium and graphite resulted in t h e carbon-diffusion-controlled formation of V2C (below approximately 2160°C) and VC scales below 2670°C. Parabolic growth behavior for both phases was observed ; the growth constant for VC was expressible as K,V" = 2.13 exp -(67,00O/RT) cm2/sec. The growth rate of V2C was lower a t 2000" than at 1900°C. T h e chemical diffusivity of carbon in VC above 2160°C was estimated to b e Dcv" = 0.26 exp -(58,30O/RT) cm2/sec. Several contributions to the vanadium-carbon binary diagram are presented. T h e VC + C eliquid eutectic point was determined to be a t C/V = 1.15 A 0.05 at 2670" =k 50°C.