The influence of heat input on the microstructure and solute segregation mechanism of invar alloy laser melting deposition process

Abstract

Laser melting deposition with different parameters was performed on invar alloy powder and substrate by KUKA Robot with a fiber laser of YSL-6000. The deposition porosity, microstructure and component enrichment behavior were studied. It revealed that the deposition porosity could be effectively controlled with laser power of 2300 W and scanning speed of 1.5 mm s−1. The microstructure evolution suffered from elongate cellular crystal to equiaxed cellular crystal, while the constitutional supercooling increased from initial solidification to final solidification. The component enrichment behavior was observed near the surface of deposition layer measured by EDS. The ferrum content near the surface reached the highest value 64.39 wt%, but only 62.52 wt% in the center. In addition, the distribution of ferrum component and Vickers hardness along the center line of deposition layer were investigated. It was also found that the component content in the top of deposition layer is highest ~57%. The decrease tendency of microhardness (in a range of 96.1 to 110.5 HV) from the bottom to the top of DL is performed. The marangoni convection behavior, that is slower velocity at the edge, is the key factor that dominated the ferrum distribution.