CRATER STRUCTURE IN ATOMIZED NICKEL SUPERALLOY ELECTRODE

The structure formed in the crater of Nl-Al-Ti-Cr-Co-W-Mo-Nb-Hf-C-B ni ckel superalloy subjected to centrifugal atomization was studied. A ma rked difference was found in the behavior of boron and carbon in the s ubsurface layer of the crater caused by the significantly deeper zone of homogeneous solid solution distribution of boron (down to 1 mm) com pared to that of carbon (0.1 mm). Cracks up to 10 mm deep were reveale d, caused. apparently, by the thermal gradient on electrode atomizatio n accompanied by the formation of liquation pores resulting from inten se boron migration to cracks and, further along cracks to the surface. The composition of boride and carbide phases was determined. The mech anism of crater structure formation was suggested.