The effect of VAR process parameters on white spot formation in INCONEL1 718.

A 20 inch diameter VAR ingot of Inconel 718 was produced at Special Metals Wiggin Limited (Hereford) under conditions of abnormally long arc gap. It was sectioned and analyzed in the as-cast state. White spots were found, along with unusual macrostructural features at the ingot surface. The experimental results are presented and discussed in relation to possible formation mechanisms, and it is shown that the level of niobium found in these white spots was too low to be explained by conventional mechanisms of formation. [ABSTRACT FROM AUTHOR]