Effect of Ti addition on cracking and microhardness of Inconel 625 during the laser solid forming processing

The effect of Ti addition on the cracking and microhardness of Ni-based superalloy Inconel 625 during the laser solid forming was investigated. With the increase of Ti content, the crack rate decreased till nil because of shrunken solidification temperature range and sufficient liquid phase healing the solidification cracks by back-filling in the terminal solidification stage. The addition of Ti promoted the formation of (γ+Laves) eutectic phase and led to the transformation of morphology of the Laves phase from the dotted or short rod to the lamellar and massive network. When the content of Ti exceeded 5 wt %, the microhardness of the alloys improved by 100 HV compared with the alloys containing below 5 wt % Ti addition. The increase in microhardness can be mainly ascribed to a network distribution of the (γ+Laves) eutectic phase.