材料期刊网

The influence of carbon and aluminium on deoxidation during vacuum induction melting (VIM) of a Ni-6Cr2-Mo-6W -5Co alloy using a CaO crucible has been studied. It has been found that carbon plays a dominant role in deoxidation during the melting stage, and about 50-70%, of the initial oxygen can be removed. Thermodynamics calculations show that the C-O reaction is far from the equilibrium state, and experimental results for carbon and oxygen contents in the liquid alloy correspond with those when the CO partial pressure p(CO) is 10(3)-10(2) Pa. Aluminium addition can further reduce the oxygen content to below 6 ppm. Thermodynamics calculations for the C-Al, Al-CaO and C-Al2O3 reactions demonstrate that they can all take place during the melting process. These reactions bring about reductions in the amounts of carbon and aluminium, respectively, of about 1.3-3.5 times and 20-50 times those required for deoxidation only.