During the process of welding overlays inside the small diameter pipe with Inconel 625 solid wire using MIG welding continuously, we find some green matter on the surface of the welding overlays. What is it? Is it some alloys burned? The length of the pipe is about 300mm, and the tempetature of the outside pipe wall is truly high, even somtimes higher than 400 deg.C. There are two layers added up.
Thank you in advance.