DEPENDENCE OF WELD HEAT AFFECTED ZONE CRACKING IN PRECIPITATIONHARDENED NICKEL BASED SUPERALLOYS ON GRAIN BOUNDARIES

摘要

The advent of single crystal (SX) and directionally solidified (DS) precipitation-hardened nickelbased superalloys has resulted in a significant increase in the thermal efficiency of gas turbines. Unfortunately, these alloys are difficult to weld due to their high susceptibility to heat affected zone (HAZ) cracking. In the present research, HAZ cracking in gas tungsten arc welded superalloys with varying γ′ content and produced by different casting techniques, was investigated. The results of the study including alleviation and elimination of HAZ cracking by reduced number of grain boundaries intersecting fusion zone boundary, owing to directional solidification during casting, are presented and discussed.