1999 Volume 17 Issue 4 Pages 534-542
The purpose of the present study was to investigate the effect of grain size on HAZ cracking susceptibility of cast alloy 718. Three kinds of base metals with three different levels of grain size were used. HAZ cracking susceptibility has been evaluated by using Spot-Varestraint test at four different strain levels. It was found that HAZ cracking susceptibility was dependent on the grain size. The length of HAZ cracking decreased with decreasing the grain size. According to Isothermal Liqaution test, smaller grain size reduced the ratio of grain boundary liquation. Microscopic observation revealed that the percentage of Laves cluster on the grain boundary was decreased with decreasing the grain size. On the basis of these results, the improvement of HAZ cracking susceptibility by smaller grain size was considered to be attributed to the reduction of Laves cluster on grain boundary.
