TIG-Based Arc Additive Manufacturing: Current Research Status and Future Prospects

Literature Overview

This comprehensive review by Guo Lixiang, Li Xiaoping, Chen Yang, Huang Jialei, Chen Jufang, and Lei Weining from Jiangsu University, published in Hot Working Technology in 2023, surveys the current state of the art in TIG-based arc additive manufacturing (AM) and outlines future research directions. As an expert who has witnessed the evolution of welding technology from conventional arc welding to modern additive manufacturing, I find this review particularly timely and insightful.

Fundamentals of TIG-Based Arc Additive Manufacturing

Arc additive manufacturing uses a concentrated heat source to melt metal powder or wire, depositing material layer by layer to build three-dimensional components. TIG-based AM, also known as TIG-AM, employs the gas tungsten arc as the heat source, with wire or powder as the feedstock material.

The fundamental process parameters include:

Parameter	Typical Range	Effect
Arc current	50–200 A	Controls deposition rate and heat input
Arc voltage	15–25 V	Influences arc stability and penetration
Travel speed	5–50 mm/min	Controls layer thickness and dilution
Wire feed rate	0.5–5.0 m/min	Matches deposition rate to arc energy
Shielding gas flow	15–25 L/min	Protects melt pool from contamination
Layer thickness	1–3 mm	Depends on wire diameter and process parameters
Powder particle size	50–150 μm	Affects flowability and deposition efficiency

Process Variants and Configuration

TIG-AM can be implemented in several configurations, each with distinct advantages and limitations:

Wire-Feed TIG-AM

Uses continuous wire as the feedstock material
Higher deposition rates (up to 5 kg/h for single wire)
Lower material cost compared to powder-based processes
Suitable for structural components and large-scale parts
Wire can be fed through the torch or from a separate wire feeder

Powder-Feed TIG-AM

Uses metal powder delivered to the arc through a powder feeder
More flexible material selection
Better surface finish and dimensional accuracy
Lower deposition rates than wire-feed
Powder utilization efficiency is typically 60–80%

Hybrid TIG-AM

Combines TIG arc with additional heat sources such as laser or plasma
Enhanced process stability and deposition rates
Improved dilution control in cladding applications
More complex equipment requirements

Technical Challenges and Solutions

Dilution Control

One of the most critical challenges in TIG-AM is controlling the dilution between the deposited material and the substrate. High dilution leads to composition changes in the deposited layers, potentially compromising the desired properties.

Dilution Level	Effect on Properties	Mitigation Strategy
< 20%	Minimal effect	Acceptable for most applications
20–40%	Moderate composition change	Adjust process parameters
40–60%	Significant property degradation	Use multiple layers or buffer layer
> 60%	Unacceptable for most applications	Redesign process or use alternative method

Residual Stress Management

The layer-by-layer deposition process generates significant residual stresses due to the thermal gradients between hot deposited layers and cooler underlying layers. These stresses can lead to:

Part warping and distortion
Cracking in the deposited layers
Reduced fatigue life of the final component

Mitigation strategies include:

Using a backing plate with controlled thermal conductivity
Applying interpass temperature control
Employing multi-pass strategies with stress-relieving passes
Post-build heat treatment

Process Stability and Arc Behavior

The TIG arc in AM operates under conditions different from conventional welding. The arc interacts with previously deposited layers, which may have different surface conditions, geometry, and thermal properties. This leads to:

Arc deflection and instability
Variable arc length and power density
Inconsistent melt pool geometry
Difficulty in maintaining consistent deposition quality

Applications in Cladding and Bimetallic Products

TIG-AM has significant potential for cladding and bimetallic product manufacturing:

Corrosion-resistant cladding: Depositing stainless steel or nickel-based alloy layers on carbon steel substrates for enhanced corrosion resistance in aggressive environments.
Wear-resistant cladding: Building up hardfacing layers with controlled composition and microstructure for improved wear resistance.
Repair and remanufacturing: Restoring worn or damaged components to original dimensions with functionally graded material properties.
Functionally graded materials: Creating components with controlled composition gradients from the substrate to the surface, optimizing both mechanical and corrosion properties.

Standards and Quality Assurance

The emerging field of arc AM requires appropriate standards for qualification and certification. Current applicable standards include:

ASTM F3001: Standard Practice for the Development of Welding Procedure Qualifications for Additive Manufacturing
ASTM F3041: Standard Practice for the Development of Welding Performance Qualifications for Additive Manufacturing
ISO 17732: Additive Manufacturing — General — Terminology
EN ISO 18435: Additive Manufacturing — General — Requirements

Quality control in TIG-AM involves:

In-process monitoring of arc voltage, current, and travel speed
Post-build inspection using RT, UT, or CT scanning
Mechanical testing of representative coupons
Microstructural analysis of critical sections
Corrosion testing for cladding applications

Key Reflections and Future Directions

Having witnessed the evolution of welding technology over six decades, I recognize that TIG-based arc AM represents a natural extension of conventional TIG welding into the realm of additive manufacturing. The fundamental physics of arc melting and solidification remain the same, but the application context and process requirements are fundamentally different.

The most promising future directions include:

Multi-wire or multi-powder TIG-AM: Enabling functionally graded materials and multi-material components in a single build.
Real-time process monitoring and control: Using arc sensing, optical monitoring, or acoustic sensing to detect and correct process deviations in real time.
Integration with robotic systems: Automating the TIG-AM process for complex geometries and large-scale components.
Development of dedicated AM-grade materials: Tailoring wire and powder compositions specifically for AM processing to optimize meltability, deposition quality, and final properties.
Standardization and qualification: Establishing comprehensive standards for TIG-AM process qualification, material certification, and quality assurance.

The convergence of TIG-AM with traditional cladding and bimetallic product manufacturing opens new possibilities for creating components with tailored surface properties, reduced material waste, and enhanced design flexibility. As the technology matures, I expect to see increasing adoption in aerospace, energy, and medical industries where custom-shaped, corrosion-resistant, or wear-resistant components are in high demand.