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Key Words: Metal Matrix Composites, Tungsten Carbide, DED-Arc Plasma, Additive Manufacturing, and Hybrid Additive Manufacturing.
This study investigates the fabrication of 316L stainless steel–WC metal matrix composites (MMCs) using a hybrid wire–powder Plasma Arc Directed Energy Deposition (DED) process. The system integrates an auxiliary powder feeder into a conventional wire-based plasma DED setup, enabling the simultaneous deposition of a 316L wire matrix and WC ceramic reinforcement. The effects of constant and variable heat input on reinforcement distribution, phase formation, and the mechanical and tribological properties of the composites were investigated.
Multi-layer wall structures were fabricated under both heat input strategies and evaluated against reference materials. Microstructural and structural characterization, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were combined with hardness, tensile, and wear testing to establish relationships between processing conditions, microstructure, and material performance.
Constant heat input produced characteristic WC accumulation along the sides of the walls, consistent with weld pool convection, whereas variable heat input promoted a more uniform reinforcement distribution. Partial WC decomposition led to the formation of M₂₃C₆ carbide networks, iron–tungsten η-carbides, and tungsten-rich eutectic constituents. Additionally, tungsten diffused into the surrounding matrix, modifying its local chemical composition.
Hardness measurements demonstrated a substantial increase in matrix hardness from approximately 180 HV0.5 in the 316L reference to approximately 370 HV0.5 in the composites, with local values approaching 800 HV0.5 near carbide particles. However, tensile properties deteriorated compared with the 316L reference samples. Angular reinforcement particles and associated stress concentrations facilitated crack propagation and promoted brittle fracture behaviour. Wear testing showed improved frictional behaviour relative to 316L.
The results demonstrate the feasibility of hybrid wire–powder Plasma Arc DED for manufacturing 316L/WC MMCs and identify heat input control as an important factor governing reinforcement distribution. They also highlight the balance between increased hardness and improved frictional behaviour and the reduction in tensile performance associated with reinforcement morphology and carbide formation.