# Modeling and Mechanistic Analysis of Molten Pool Evolution and Energy Synergy in Laser–Cold Metal Transfer Hybrid Additive Manufacturing of 316L Stainless Steel

## TL;DR

This paper studies how spatial orientation affects molten pool behavior in laser-CMT hybrid 3D printing, improving simulation accuracy and process optimization.

## Contribution

A self-adaptive CMT arc heat source model was developed to better simulate laser-CMT hybrid additive manufacturing processes.

## Key findings

- Gravity direction has limited impact on molten pool shape but affects local convection and temperature gradients.
- Simulations revealed keyhole formation, dual-vortex flow, and Marangoni-driven circulation in molten pools.
- Optimized heat input reduces thermal stress and improves layer bonding in multi-layer deposition.

## Abstract

What are the main findings?
Developed a self-adaptive CMT arc heat source for laser–CMT hybrid modeling.Provided insight into orientation-governed thermal and flow field mechanisms.Revealed orientation-dependent molten pool flow and temperature evolution.

Developed a self-adaptive CMT arc heat source for laser–CMT hybrid modeling.

Provided insight into orientation-governed thermal and flow field mechanisms.

Revealed orientation-dependent molten pool flow and temperature evolution.

What are the implications of the main findings?
Enables higher simulation fidelity in predicting complex multiphysics interactions for hybrid directed energy deposition.Provides practical guidelines for optimizing process parameters and scanning strategies to control deposition quality.

Enables higher simulation fidelity in predicting complex multiphysics interactions for hybrid directed energy deposition.

Provides practical guidelines for optimizing process parameters and scanning strategies to control deposition quality.

The present work uses numerical methods to explore the impact of spatial orientation on the behavior of molten pool and thermal responses during the laser–Cold Metal Transfer (CMT) hybrid additive manufacturing of metallic cladding layers. Based on the traditional double-ellipsoidal heat source model, an adaptive CMT arc heat source model was developed and optimized using experimentally calibrated parameters to accurately represent the coupled energy distribution of the laser and CMT arc. The improved model was employed to simulate temperature and velocity fields under horizontal, transverse, vertical-up, and vertical-down orientations. The results revealed that variations in gravity direction had a limited effect on the overall molten pool morphology due to the dominant role of vapor recoil pressure, while significantly influencing the local convection patterns and temperature gradients. The simulations further demonstrated the formation of keyholes, dual-vortex flow structures, and Marangoni-driven circulation within the molten pool, as well as the redistribution of molten metal under different orientations. In multi-layer deposition simulations, optimized heat input effectively mitigated excessive thermal stresses, ensured uniform interlayer bonding, and maintained high forming accuracy. This work establishes a comprehensive numerical framework for analyzing orientation-dependent heat and mass transfer mechanisms and provides a solid foundation for the adaptive control and optimization of laser–CMT hybrid additive manufacturing processes.