Effects of phosphorus content on stress-rupture and creep properties of IN718

The effect of phosphorus on IN718 alloy was studied. The results showed that phosphorus can significantly affect the stress-rupture properties. With increasing content of phosphorus from 0.003% to 0.03%, the stress-rupture life increases firstly and then decreases and reaches the peak value at 0.025%. Phosphorus does not appears to modify the stress exponent but influences the apparent activation energy for creep markedly. The beneficial effects of phosphorus mainly arise from the suppression of diffusion along grain boundary and the improvement of grain boundary δ-phase.