In current research, WC dissolution phenomenon happened in TIG welds was investigated and discussed. And the element diffusion was studied using area-scanning method. The results showed that the WC dissolution phenomenon always happened near WC-Co/Welded seam interface. Moreover, the amount of WC dissolved in welds became less from WC-Co, welds to invar alloys. WC dissolution happened in welded seam induced by tungsten arc led to the WC grain growth (60µm or so) and WC shape changes. The grain boundary (GB) between different WC particles during WC aggregation was also confirmed and WC grain growth was owed to the WC aggregation during the processing of WC dissolution.