1988 Volume 6 Issue 4 Pages 530-536
Carbide precipitation in niclel based alloy takes place at elevated temperature. The tendency of this phenomenon is stronger than in austenitic stainless steel. But the carbide precipitation in HAZ of nickel based alloy has not been investigated enough as that of austenitic stainless steel.
The effect of weld thermal cycle on carbide precipiration of 15Cr-75Ni alloy (UNS N06600) and its relation with intergranular corrosion in nitric acid were investigated. And prevention of sensitization in HAZ was investigated from the view point of chemical composition.
The susceptibility to intergarnular corrosion in HAZ agreed with the carbide behavior during weld thermal cycle and aging so far as the aging heat treatment condition of this work. The carbide in the base metal overaged is solid soluted and nucleates at the grain boundary by weld thermal cycle, and the carbide precipitated and grew during aging. The chrominm depleted zone has not healed after aged for 15 hours at 823K, so the carbide caused the intergranular sensitization.
The sensitization in HAZ of 15Cr-75Ni Alloy can be prevented by the suitable addition of Nb; Nb/ C<40 in weight ratio.