High-reliability repair of single-crystal Ni-base superalloy by selective electron beam melting

Here, we report the utilisation of a powder-bed-fusion additive manufacturing to achieve CMSX-4 single-crystal repair with René N5 powders. The is characterised by fine columnar dendritic substructure, limited in-grain misorientation over tens millimetres in height, and strong deposit-to-substrate bonding. brighter contrast region 300 400 μm thick, formed cellular solidification front, sits above melted back horizontal low-angle boundary (4° misorientation) in-between. Its higher hardness 450 HV attributed cuboidal primary γ′ 135 ± 7 nm. Their presence combined effect high cooling rate local compositional difference. Scheil-Gulliver predicted solute partitioning Ta Hf inter-dendritic agrees well MC carbides appearing at boundaries. Computational-fluid-dynamics (CFD) simulations, minimum undercooling criterion, helps determine vertical distance between melt-pool bottom oriented-to-misoriented transition borderline, providing convenient guideline assess likelihood, sense that this needs be larger than hatch depth. CFD-calculated velocities thermal gradients agree columnar-to-equiaxed curve experimental observation.