Research Status and Prospects of TIG Welding-Based Arc Additive Manufacturing

Literature Overview

This paper, authored by Guo Lixiang et al. from Jiangsu University of Science and Technology and published in Hot Working Technology (2023, Vol. 52, No. 5, pp. 7-12), provides a comprehensive review of Wire Arc Additive Manufacturing (WAAM) based on Tungsten Inert Gas (TIG) welding. The authors systematically summarize the current state of process parameter optimization, thermal accumulation management, and auxiliary manufacturing strategies, while also identifying key challenges and future research directions.

Core Technical Characteristics of TIG-WAAM

Why TIG over Other Arc Processes

Among the various arc processes employed in WAAM (SMAW, GMAW, FCAW, and TIG), TIG-based WAAM offers several distinctive advantages:

The spatter-free nature of TIG welding is particularly advantageous for additive manufacturing, where clean deposition layers are essential for dimensional accuracy and surface quality. The high material utilization rate reduces post-processing costs and improves economic viability, especially for expensive materials such as titanium alloys and nickel-based superalloys.

Process Parameters and Their Effects

Current and Arc Power

The welding current directly controls the heat input and thus the dilution rate, penetration depth, and microstructure of each deposited layer. Typical TIG-WAAM current ranges from 100 to 300 A for steel wire feed. Higher currents increase deposition rate but also increase thermal input, leading to coarser grain structures and potential interlayer defects. The optimal current must balance deposition efficiency with microstructural quality.

Travel Speed and Layer Geometry

Travel speed determines the bead width, height, and overlap between adjacent passes. A slower travel speed produces wider, taller beads with higher dilution, while faster speeds yield narrower beads with lower dilution. The inter-pass gap and overlap ratio (typically 30–50%) are critical for ensuring metallurgical bonding between layers. Insufficient overlap results in lack-of-fusion defects, while excessive overlap causes thermal accumulation and distortion.

Shielding Gas

Argon is the most commonly used shielding gas, providing excellent arc stability and penetration. Helium or argon-helium mixtures (e.g., 75Ar/25He) increase arc energy and penetration depth, beneficial for thick-section deposition. The gas flow rate (typically 15–25 L/min) must be sufficient to prevent atmospheric contamination while avoiding turbulence that could disrupt the arc.

Wire Feed Angle

The wire feed angle relative to the welding direction (typically 5–20° forward tilt) affects the arc force distribution, bead profile, and droplet transfer stability. A slight forward angle improves arc stability and bead uniformity, while a vertical feed angle may be preferred for specific geometric configurations.

Thermal Accumulation and Bead Deviation

Thermal Accumulation Challenge

One of the most significant challenges in TIG-WAAM is thermal accumulation, which results from the sequential deposition of multiple layers without complete cooling between passes. This leads to:

• Elevated interlayer temperatures that reduce the effective cooling rate of subsequent layers.
• Coarsening of grain structure and softening of the deposited material.
• Distortion and warping of the build plate and deposited geometry.
• Potential interlayer lack-of-fusion when the previous layer is not sufficiently solidified.

Bead Deviation

Bead deviation refers to the lateral displacement of deposited material from the intended path, caused by thermal gradients, gravity effects, and magnetic arc forces. In tall vertical builds, cumulative bead deviation can exceed 2–3 mm per layer, leading to dimensional inaccuracy and surface roughness. Countermeasures include:

• Active cooling between layers (air cooling, water cooling, or induction quenching).
• In-situ monitoring and real-time path correction.
• Optimized deposition strategies (e.g., zigzag, serpentine, or spiral patterns).
• Reduced layer height to minimize thermal input per layer.

Pre-Treatment and Auxiliary Manufacturing Strategies

Pre-Treatment Methods

• Wire preheating: Preheating the wire to 100–300°C reduces thermal gradient between wire and deposited layer, improving metallurgical bonding.
• Build plate preheating: Preheating the substrate to 150–400°C reduces residual stress and prevents cracking in high-strength steels.
• Wire cleaning: Mechanical or chemical cleaning of the wire surface removes oxide layers and contaminants that could cause porosity.

Auxiliary Manufacturing Integration

The authors highlight the integration of WAAM with traditional machining, heat treatment, and surface engineering:

• Post-deposition machining: Milling, turning, or grinding to achieve final dimensional accuracy and surface finish.
• Heat treatment: Solution treatment and aging to homogenize microstructure and improve mechanical properties.
• Surface engineering: Shot peening or laser texturing to introduce compressive residual stresses and improve fatigue life.

Future Research Directions

The paper identifies several promising research avenues:

1. Multi-wire TIG-WAAM for simultaneous deposition of dissimilar materials or gradient composites.
2. Integration of in-situ monitoring (thermography, acoustic emission, machine vision) for closed-loop process control.
3. Development of novel wire materials (e.g., high-entropy alloy wires, functionally graded wires) to expand the range of achievable properties.
4. Scale-up to large-scale structural components for aerospace, shipbuilding, and energy sectors.
5. Standardization of process parameters and qualification procedures for industrial certification.

Study Insights

This review provides a valuable roadmap for engineers entering the TIG-WAAM field. The emphasis on spatter-free deposition and high material utilization positions TIG-WAAM as a strong candidate for producing high-value components from expensive materials. However, the thermal accumulation problem remains the primary barrier to producing large, defect-free components. Future work should focus on developing hybrid cooling strategies that combine interlayer active cooling with optimized deposition sequences. The integration of WAAM with conventional manufacturing (hybrid manufacturing) will likely be the most practical path to industrial adoption in the near term, leveraging the flexibility of additive processes while maintaining the quality assurance of traditional methods.