1982 Volume 51 Issue 12 Pages 989-995
In this study, the effect of Nb/C on the sensitivity of liquation cracking of 24Cr-24Ni-1.5Nb Fe-base heat resisting alloy (IN-519) was researched at first. Then, metallurgical inspections on various phases at grain boundaries were conducted. Solidification phenomena of this alloy were also examined. The main results obtained in this experiment are as follows;
1) The sensitivity of liquation cracking of this alloy becomes minimum when the value of Nb/C is about 1.0. Its sensitivity increases in the case of Nb/C value decreasing less than about 1.0 or increasing more than about 1.0. When Nb/C value decreases less than about 1.0, Cr carbide-r solid solution eutectics are formed at grain boundaries besides NbC-r solid solution eutectics. As the solidification temperature of Cr carbide-r solid solution eutectic is lower compared with that of NbC-r solid solution eutectic, the solidification cracking sensitivity increases. When Nb/C value increases more than about 1.0, Laves phase-r solid solution eutectics of which solidification temperatures are lower than those of NbC eutectics, are formed at grain boundaries. So, the sensitivity of liquation cracking of this alloy increases again.
2) To improve the resistivity to liquation cracking of this alloy, increasing Nb content and decreasing C content are very effective.
