been recognised for about 70 years. Merica and Waltenberg2 attributed the effect of S to the formation The present state of knowledge on the effects of C, of a low melting point eutectic with Ni. Similarly, B, S, and P on the weldability of Ni base superalloys is reviewed. Consideration is also White et al.3 quoting some Russian work have shown given to the effects of Mg and the rare earths on reduced values of reduction in area with increasing S weldability, though the data are sparse and the concentrations (10-140 at. ppm) in Ni in the tempermanufacturing route often not defined. From the ature range 600-1000°C (Fig. 1). A considerable analysis, B is considered to be the most influence of S on ductility is seen when Á20 ppm of detrimental element to the weldability, with lesser S is added to the Ni. effects from C and S. The data on P are limited, but The effects of minor elements on the weldability of recent results show that P has a variable effect on superalloys have been investigated since the 1950s, weldability, being most detrimental in low C alloys with the research of Pease,4 for example, showing (0•01 wt-%), and less of a problem in C levels that P, S, and B were detrimental. Carbon was >0•03 wt-% and above. Consideration is also given to the effects of heat treatment in influencing considered to have a variable effect along with Al, Ti, solute segregation to the grain boundary and on Mo, and Si. Magnesium was considered beneficial, grain growth. The potential effects of two or more though Zr was considered detrimental. Pease's results elements on grain boundary microchemistry and formed the basis for minor element control in the its effects on weldability are also discussed. early days of superalloy metallurgy, especially for IMR/347 wrought air melted alloys of Ni.In the literature, results of the research on the effect
