H-phase sulphocarbides and sulphur in nickel-base superalloys

H-phase sulphocarbides of the M₂SC type, occurring in the cast nickel-base superalloys IN 100 and 713LC, have been isolated and characterized by X-ray diffraction and electron probe microanalysis. The lattice parameters for the M₂SC phase in IN 100 were: a=3'24 Å, c=11·30 Å, and in 713LC were: a=3·365 Å, c=11·95 Å. The M radical for the M₂SC phase in IN 100 was predominantly titanium, while in 713LC it was predominantly zirconium. IN 100 contained a larger volume fraction of sulphocarbide particles than 713LC, even though the sulphur contents of the two alloys were nominally similar. It is concluded that one contribution of titanium and zirconium additions to nickel-base superalloys is to act as scavengers for residual sulphur, and that hafnium additions may act similarly.