Cracking behavior and control of Rene 104 superalloy produced by direct laser fabrication

Direct laser fabrication (DLF) technology based on blowing powder has been used to manufacture Rene 104 superalloy with a high cracking sensitivity. The manufacturing processes, post-treatment of hot isostatic pressing (hipping), microstructure and crack characterization of the DLFed Rene 104 samples deposited at various volume energy densities are presented. The results show that the cracking sensitivity closely depends on the heat input and increases with increasing volume energy density from 429 to 827 J/mm3. The optimization of parameters by adopting large hatch spacings in combination with moderate laser powers can only reduce but not eliminate the cracks in the Rene 104 cuboid samples. Cracking mechanisms including solidification cracking, grain boundary liquation cracking and ductility dip cracking are proposed based on the composition of Rene 104 and processing characteristics to explain the cracking behavior of the Rene 104 superalloy during DLF. Finally, Rene 104 superalloy parts free from cracks and with sound microstructures can be manufactured at optimized DLF processing parameters followed by hipping treatment.