Effect of grain boundary composition on tensile strength and hydrogen induced stress corrosion cracking of Ni–20Cr

The grain boundary segregation of P and C in Ni–20Cr (wt-%) was investigated using Auger electron spectroscopy for specimens aged in the temperature range 500–700°C after fracture by a tensile test inside an ultra high vacuum chamber. At the grain boundaries, C segregates first and then is partly displaced by P; on continued aging, precipitation and growth of carbides occurs. High P contents initiate the formation of Cr₂₃C₆ instead ofCr₇C₃. The correlation of these processes with the tensile strength is demonstrated and their influence on the stress corrosion cracking in a slow strain rate test during charging with hydrogen is examined.

MST/1195