Investigation on the Morphology and Formation Mechanism of Porosity in Different Heat Source Regions of Nickel-Based Alloy Laser Hybrid Welding.

The cross section of the laser-melt inert gas welding (MIG) hybrid welding joint can be divided into two different heat source regions, the upper is the laser-MIG hybrid heat source region, and the lower is the laser heat source region. In this paper, the laser-MIG hybrid welding experiments were carried out on a new nickel-based alloy 4716MA0. The type, morphology and distribution characteristics of porosity in different heat source regions were researched by optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy. In addition, the formation mechanism of different types of stomata was explained by the model diagram. It is found that the dominant region of the laser-MIG hybrid heat source is dominated by metallurgical porosity, which is attributed to the formation of CO gas, whereas the dominant area of the laser heat source is dominated by process porosity. The generation of process porosity is attributed to the instability of the keyhole. [ABSTRACT FROM AUTHOR]