Numerical modeling of thermal behavior of melt pool in laser additive manufacturing of Ni-based diamond tools

Abstract

In this paper the heat absorption, heat transfer and solidification evolution of melt pool in the laser additive manufacturing of Ni–Cr metal bonded diamond tools were studied. Based on the ray tracing theory, the influence of diamond and Ni–Cr alloy powder parameters on laser energy absorptivity was analyzed and the temperature model of mixed powder bed was constructed. Combined with the model and experiment, the impact of the diamond itself and its arrangement on the temperature distribution and shape of melt pool was explored and compared. The change rule of melt pool and microstructure in laser multi-track scanning was investigated. The evolution of melt pool solidification and microstructure with the influence of diamond was revealed. The results show that the powder thickness has a great influence on laser energy absorptivity. The diamond has obvious influence on the temperature distribution and geometry of melt pool, and the influence degree and variation rule are related to the diamond arrangement and position. In the process of laser multi-track scanning, the temperature increases and the geometry of melt pool enlarges gradually. Near the diamond, the diamond changes the direction of temperature gradient of metal melt, accelerates crystals solidification, makes the growth direction of crystals approximately perpendicular to diamond, and increases the endogenetic nucleation phenomenon of crystals near the diamond interface.