Effect of minor elements on weldability of nickel base superalloys

The present state of knowledge on the effects of C, B, S, and P on the weldability of Ni base superalloys is reviewed. Consideration is also given to the effects of Mg and the rare earths on weldability, though the data are sparse and the manufacturing route often not defined. From the analysis, B is considered to be the most detrimental element to the weldability, with lesser effects from C and S. The data on P are limited, but recent results show that P has a variable effect on weldability, being most detrimental in low C alloys (0·01 wt-%), and less of a problem in C levels >0·03 wt-% and above. Consideration is also given to the effects of heat treatment in influencing solute segregation to the grain boundary and on grain growth. The potential effects of two or more elements on grain boundary microchemistry and its effects on weldability are also discussed.