EFFECT OF PROCESSING TECHNIQUE ON WELDABILITY OF IN738 ALLOY
Abstract
The weldability of IN738 alloy processed by two different casting techniques, viz., conventional casting and directional solidification, was investigated by using autogenous bead-on-plate laser beam welding. Microstructural analysis of the welded samples showed that in both the materials, cracking occurred mainly in the heat affected zone (HAZ). However, the amount of HAZ cracking was observed to be significantly greater in the conventionally cast polycrystalline alloy than that in the directionally solidified (DS) alloy. Besides, cracking in directionally solidified material was observed to be minimum in samples welded in a direction perpendicular to the solidification direction (i.e. the transverse direction), compared to when welding was done parallel to the solidification direction (i.e., the longitudinal direction). The results of this research indicated that an increase in grain size, that is, a reduction in the number of grain boundaries, particularly the transverse grain boundaries, in the material produced by directional solidification vis-à-vis the conventionally cast material can significantly alleviate the problem of HAZ cracking in IN738 superalloy.
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References
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