Wr. Sun et al., EFFECT OF PHOSPHORUS ON THE MICROSTRUCTURE AND STRESS RUPTURE PROPERTIES IN AN FE-NI-CR BASE SUPERALLOY, Metallurgical and materials transactions. A, Physical metallurgy andmaterials science, 28(3), 1997, pp. 649-654
This article describes the effect of phosphorus on the microstructure
and stress rupture property at 650 degrees C in an Fe-Ni-Cr base super
alloy. The results showed that phosphorus markedly improved the interg
ranular precipitation in the range of 0.0005 to 0.016 wt pet, which fa
cilitated M(23)C(6) and M(3)B(2) precipitation but inhibited the forma
tion of MC carbide. A too high phosphorus addition (0.051 wt pet P) re
sulted in an excessive precipitation at grain boundaries, while a too
low phosphorus content (0.0005 wt pet P) led to many precipitate-free
grain boundaries. Phosphorus also enlarged the size of the gamma' part
icles and lowered its stability, that eta-Ni3Ti preferred to form in t
he alloy with 0.051 wt pet P. Due to the improvement of the microstruc
ture, appropriate amount of P content significantly prolonged the rupt
ure life of the alloys in the range of 0.0005 to 0.016 wt pet. The pea
k value was 660 hours at 0.016 wt pet, more than 4 times that of the a
lloy with 0.0005 wt pet phosphorus, but phosphorus reduced the fractur
e elongation. The mechanism by which phosphorus influenced the alloy i
s discussed.