Metallurgical Characteristics and Optimum Casting Conditions on VADER Process

The VADER (Vacuum Arc Double Electrode Remelting) process introduced by Special Metals Corp. in 1982 is a noticeable new vacuum melting and casting technology. This process has potential as an alternative for powder metallurgy in superalloy production, because the as cast VADER ingot might be forged directly due to the uniform fine grain structure and low level of macro-segregation.Metallurgical characteristics of VADER process such as formation mechanism of molten metal droplets, optimum casting conditions and hot workability of as cast ingot were studied by melting and casting stainless steel and Ni-base superalloy using an experimental VADER equipment.Fine grain structure of 100-200 μm free of micro void was obtained under conditions of low super-heat of molten metal droplets (1030°C) and low casting speed (several cm/min) in the case of 90200mmφ ingots cast into steel molds. The hot workability of as cast Ni-base superalloy ingot was equal to that of forged material.