The atomic percent of each pure metal in the alloy are converted to mass percent, weighed out, and placed into a hemispherical hole in the arc melter container, in an order determined by their relative metling points – for example, a lower melting point material should be covered by the others, to avoid vaporisation and loss of material, changing the composition of the melted alloy. Alongside the weighed out metal, a piece of material with high oxygen affinity (a ‘getter’), for example titanium, is placed into the chamber. The air is then evacuated from the arc melter, and a current is passed between two electrodes. This forms a high temperature plasma arc of temperature variable with current, which is used to melt the metals. First, the getter is melted, to absorb any residual oxygen remaining in the chamber after evacuation, in order to further minimise oxidation of the melted alloy. The getter is melted on one side, before being flipped and re-melted on the opposite side. This process is repeated four times to ensure a thorough melt. This process is then repeated with the weighed out metal, until an irregularly-shaped blob of fully melted alloy is obtained. A variable polariser should be used at the window to the chamber, in order to both allow the user to assess the quality of the melt, and also protect their eyes from the bright plasma arc when the current is active.
Ferritic/Titanium superalloys and refractory materials