Solidification cracking susceptibility and carbide evolution behavior in ERNiMo-2 weld metal: Effect and mechanism of Si content

ERNiMo-2 wire is the matching welding filler metal for the GH3535 alloy, which is prone to occur solidification cracking during welding. Optimizing the composition of ERNiMo-2 wire is an effective way to reduce the welding solidification cracking susceptibility (WSCS) and improve the performance of GH3535 alloy welded joint. In this study, the WSCS of ERNiMo-2 wires with different Si content was evaluated by the trans-varestraint test, and the mechanism of Si affecting the weldability of ERNiMo-2 wire was revealed. The results showed that the solidification cracking temperature range (SCTR) of Si1-Si4 wires with Si content increasing is 102 °C, 123.2 °C, 119.1 °C and 116.3 °C, respectively. The existence of eutectic M2C and M6C in the form of liquid film at the end of solidification leads to partial wetting of the grain boundary, which reduces the binding force of the grain boundary and promotes crack initiation. Low solidification shrinkage, thermal shrinkage, solidification temperature range and a small amount of eutectic liquid in the mushy region make the Si1 wire have the best resistance to solidification cracking. The aforementioned factors increase with Si content, then resulting in the increase of WSCS of Si2. However, the amount and fluidity of eutectic liquid in weld metal increase when the Si content increases to Si3 and Si4, which leads to the occurrence of eutectic backfilling and decrease in WSCS of ERNiMo-2 wire.