Abstract

Wire-Laser Metal Deposition (W-LMD) is a transformative direct energy deposition additive manufacturing technology that utilizes a laser heat source to melt metallic wire feedstock for the high-efficiency fabrication of large-scale, near-net-shape components. The technology is distinguished by its high material utilization efficiency and superior safety compared to metal powder-based systems. W-LMD systems are composed of a focused laser, a wire feeder mechanism, a multi-degree of freedom motion system, cooling system, and a shielding gas supply to prevent oxidation. Deviation in process parameters can lead to external defects such as stubbing (insufficient melting) and dripping (melting above the melt pool), as well as internal defects such as porosities. A key feature of W-LMD is its capability to fabricate bimetallic structures with tailored mechanical properties. Although various studies have investigated bimetallic structures using different metal additive manufacturing technologies, gaps remain in understanding the behaviour of W-LMD-fabricated bimetallic structures and the influence of deposition strategy and post-processing conditions on their mechanical performance. This work reviews key studies on W-LMD systems and their advancements in bimetallic fabrication, highlighting current research gaps and future research directions. It then investigates the effects of laser power, wall configuration, and post-deposition heat treatment on the mechanical behaviour of W-LMDfabricated ER70S-6 mild steel and SS316L stainless steel bimetallic walls. Two wall configurations were evaluated: a conventional horizontal configuration consisting of a single interface between the two materials, and a side wall configuration composed of parallel interfaces extending through the build height. A full-factorial experimental design was implemented using three laser power levels (800, 1000, and 1200 W) and three heat treatment conditions (as-built, 600°C, and 1060°C). Tensile testing was conducted, with the data analysed using Analysis of Variance (ANOVA) and Grey Relational Analysis (GRA). Results demonstrated strong metallurgical bonding between ER70S-6 and SS316L, with fracture occurring in the weaker ER70S-6 region rather than at the interface for horizontal wall configurations. Wall configuration was identified as the most influential factor affecting ultimate tensile strength (UTS), yield strength, toughness, and strain at fracture. Side wall configurations achieved substantially higher strength and toughness due to improved load sharing between both materials, whereas horizontal walls exhibited superior ductility. Increasing laser power generally enhanced tensile and yield strengths, while annealing at 1060°C significantly improved the overall mechanical performance through stress relief, recrystallization, and microstructural homogenization. GRA identified the combination of 1000 W laser power, side wall configuration, and 1060°C annealing as the optimum parameter set, providing the most balanced performance across all mechanical responses. The optimum specimen achieved a UTS of 874 MPa and a strain at fracture of 27%, outperforming several comparable directed energy deposition bimetallic steel structures reported in the literature.

Publication Date

7-2026

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering

Advisor

Salman Pervaiz

Advisor/Committee Member

Wael Abdel Samad

Advisor/Committee Member

Umer Javed

Comments

This thesis has been embargoed. The full-text will be available on or around 7/22/2027.

Campus

RIT Dubai

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