Deoxidation Equilibrium of Silicon in Liquid Nickel-Chromium, Nickel-Molybdenum and Nickel-Tungsten Alloys

Abstract

In order to understand the effect of various alloying elements on the equilibrium constant of the doeixidation of liquid nickel, the doexidation of nickel based alloys with silicon has been measured at tempertures between 1550 and 1650°C by the use of quartz crucibles.
In nickel-chromium alloys containing 0.65 mass% silicon, the deoxidation product, log K'_Si(Ni-Cr) (=[%Si][%O]²), which drastically increased by the addition of chromium until 20 mass%, was empirically represented to be:log K'_Si(Ni-Cr) = log K_Si(Ni) + 0.347[%Cr] – [%Cr]²below 15 mass% chromium, while the deoxidation product in nickel-molybdenum alloys containing 0.65 mass% silicon, log K'_Si(Ni-Me), which also linearly increased with the increase of molybdenum content up to 16 mass%, was given the expression:log K'_Si(Ni-Mo) = log K_Si(Ni) + 0.047[%Mo]In nickel-tungsten alloys bearing 0.4 mass% silicon, the value of the deoxidation product was found to be as follows:log K'_Si(Ni-W) = log K_Si(Ni) + 0.007[%W]up to 11 mass% tungsten.
For the effect of the alloying elements on the activity coefficient of oxygen in nickel, the following parameters wre obtained:log f_O(Ni)^Cr= – 0.171[%Cr]     Cr<5 mass%
log f_O(Ni)^Mo= – 0.025[%Mo]    Mo<16 mass%
log f_O(Ni)^W = – 0.004[%W]     W<11 mass%