CLADDING TECHNOLOGY SHANXI CO., LTDTIG Arc Additive Manufacturing of TC4 Titanium Alloy Frame Structures
Literature Overview
This research by Ma Qian, Ma Shuyuan, Liu Changmeng, and Chen Guangsen from Beijing Institute of Technology and the Ordnance Engineering Academy was published in Hot Working Technology in 2018. The study focuses on the TIG arc additive manufacturing (WAAM) of TC4 (Ti-6Al-4V) frame-type structural components, addressing both the process feasibility and the mechanical performance of the manufactured parts.
Core Technical Concept
Wire arc additive manufacturing using TIG as the heat source represents a cost-effective alternative to laser-based AM systems for titanium alloy components. The TIG arc provides a relatively large, stable heat source with moderate energy density (typically 5–20 kW/cm²), which is lower than laser systems but sufficient for titanium alloy deposition. The key challenge in TC4 WAAM is managing the substantial residual stresses and thermal distortions inherent in layer-by-layer deposition, particularly for frame structures with complex geometries and thin walls.
Process Parameters for TC4 WAAM
| Parameter | Typical Value | Effect on Deposition |
|---|---|---|
| Wire feed rate | 200–400 mm/min | Controls deposition rate |
| Travel speed | 500–2000 mm/min | Affects layer quality |
| Welding current | 80–150 A | Determines heat input |
| Arc voltage | 14–20 V | Controls wire melting |
| Shielding gas flow | 15–25 L/min | Prevents oxidation |
| Interpass temperature | 150–350 °C | Controls microstructure |
| Layer thickness | 1.5–3.0 mm | Affects build accuracy |
The TC4 frame structure studied likely involves multiple overlapping beads arranged to form a structural frame, requiring careful planning of the deposition sequence to minimize residual stress accumulation.
Microstructure and Mechanical Properties
The microstructure of TIG-WAAM TC4 typically exhibits a basket-weave pattern of acicular alpha and beta phases, similar to that produced by conventional welding. However, the repeated thermal cycling during layer-by-layer deposition creates a unique microstructural evolution:
- Upper layers: Coarser basket-weave structure due to lower cooling rates.
- Lower layers: Finer acicular structure due to heat dissipation into the build plate.
- Interface regions: Possible formation of Widmanstätten patterns with varying alpha colony widths.
The mechanical properties typically show anisotropy, with tensile strength varying by 10–20% between the build direction and the build direction. For TC4 produced by TIG WAAM, typical values include:
| Property | Typical Range | Comparison to Forged TC4 |
|---|---|---|
| Ultimate tensile strength | 850–1100 MPa | Comparable or slightly lower |
| Yield strength | 700–950 MPa | Comparable |
| Elongation | 8–15% | Slightly lower |
| Hardness | 320–380 HV | Comparable |
Engineering Implications for Pressure Vessel Components
The application of TIG WAAM to titanium alloy components has direct relevance to bimetal pressure vessel fabrication, particularly for:
- Titanium-lined pressure vessel repair: Localized repair of damaged cladding layers without requiring full replacement.
- Custom-shaped titanium components: Manufacturing of complex geometries such as nozzle attachments, internal structures, or heat exchanger internals.
- Rapid prototyping of titanium pressure vessel components: Enabling faster design iteration for specialized applications.
The primary concern is ensuring that the AM-produced component meets the qualification requirements of applicable standards. Current standards such as ASME VIII Div.1 and GB/T 150 do not yet fully address AM-produced components, making this research particularly valuable for future standard development.
Key Reflections
This work highlights the practical viability of TIG-based WAAM for titanium alloy structural components. From a pressure vessel engineering standpoint, the technology offers a pathway to manufacture complex titanium components that would otherwise require expensive machining from solid stock or extensive fabrication from flat sheets. The key challenge remains achieving consistent mechanical properties throughout the build volume and developing appropriate non-destructive testing methods for AM-produced titanium components.