Exploration of the power-powder-molten pool (PPM) interaction mechanism in laser deposition additive manufacturing (LDAM) process

Due to advantages of metallurgical bonding, minimal stress and distortion and comparable mechanical properties with traditional processing method, Laser Deposition Additive Manufacturing (LDAM) has become one of the core technologies in laser additive remanufacturing, metallic coating, and special components fabrication. Although LDAM process offers plenty of advantages over conventional fabrication technologies, the part quality may vary significantly even with slight variations of the input parameters. In addition, the material deposition process is hard to control due to the lack of understanding of the dynamic processes in the laser molten pool, such as particle-gas interaction, power-powder interaction and molten pool-substrate interaction. In order to achieve compact and sound deposited layers, to realize high level fabrication and remanufacturing, as well as to interpret the property variations under different experimental conditions, theses dynamic processes need to be fully understood. This research aims at discovering the interaction mechanism of power-powder-molten pool (PPM) during material deposition process through the fundamental studies on the power absorption by the powder stream and energy requirement of molten pool. This research focuses on LDAM process of Nickel-based super alloy (Inconel 718). Three highly interrelated tasks were performed: 1) investigation of the molten pool energy requirement in LDAM of Inconel 718, to acquire an energy density interval so as to obtain the desired material properties; 2) investigation of the powder stream distribution under four jet exit nozzles, to figure out the powder concentration at different positions below the deposition head; and 3) investigation of the power absorption by the powder stream through stepwise heating method, to reveal the relationship between the material properties, input parameters and power absorption for Inconel 718. The outputs of the research could help to interpret the variations of mechanical property occurred in LDAM process and to predict the correct processing conditions for other materials.