Mechanism of yttrium in deep desulfurization of NiCoCrAlY alloy during vacuum induction melting process

In this study, yttrium as desulfurizer on the purification of Ni–20Co–20Cr–10Al–Y alloy during vacuum induction melting (VIM) process using YO crucibles was investigated experimentally. It is found that Y plays an important role on the desulfurizing of the NiCoCrAlY alloy. Without any addition of Y, merely the employment of YO crucibles could effectively reduce S content of the alloy melts from 28 × 10 to 6 × 10–7 × 10. With addition of 0.8 wt% Y in the alloy, the concentration of S could further reduce 2 × 10–3 × 10. The primary interactive mechanism between Y and molten alloy was concluded to be the synthesis reaction of NiY phase, YS phases and YAlO phase. In the desulfurize slags, YS phases and YAlO phase are found. No secondary contamination is present in the alloy melts after addition of Y.