CLADDING TECHNOLOGY SHANXI CO., LTDNumerical Simulation and Experimental Study of Coaxial Powder Feeding TIG Cladding
Literature Overview
This 2023 research by Wang Wanwan, Gao Hui, Zhou Canfeng, and Li Wenlong from Beijing Institute of Chemical Technology focuses on the coaxial powder feeding TIG cladding process, combining numerical simulation with experimental validation. The work addresses a modern cladding technique that has gained significant traction in the repair and enhancement of pressure vessel internals, heat exchanger tubes, and hydrogenation reactor components where corrosion-resistant overlay layers are required.
Process Principle and Configuration
Coaxial powder feeding TIG cladding operates by directing welding powder through the central channel of the tungsten electrode or through a separate nozzle concentric with the arc. The powder particles are melted by the TIG arc and deposited onto the substrate, forming a dilution-controlled overlay layer. The coaxial configuration provides several advantages over conventional powder feeding approaches:
- Superior powder delivery stability and consistency
- Reduced arc disturbance from powder stream
- Better control of dilution ratio between substrate and deposited material
- Capability for multi-pass cladding with uniform layer thickness
Numerical Simulation Methodology
The numerical model employed in this study typically incorporates the following coupled physics:
| Modeling Component | Governing Equation | Key Assumptions |
|---|---|---|
| Heat transfer | Fourier's heat conduction equation | Temperature-dependent properties |
| Fluid flow | Navier-Stokes equations | Incompressible flow in weld pool |
| Mass transport | Species diffusion equation | Dilution controlled by convection |
| Powder trajectory | Particle dynamics model | Single-phase gas flow around particles |
| Solidification | Scheil-Gulliver model | Non-equilibrium solidification |
The simulation typically predicts the weld pool geometry, temperature distribution, dilution ratio, and solidification behavior. The key output parameter is the dilution ratio, which directly determines the chemical composition and hence the corrosion resistance of the cladding layer.
Experimental Parameters and Results
| Parameter | Value Range | Effect on Cladding Quality |
|---|---|---|
| Arc current | 80-200 A | Higher current increases dilution |
| Powder feeding rate | 20-80 g/min | Higher rate decreases dilution |
| Travel speed | 200-600 mm/min | Higher speed decreases dilution |
| Powder-to-current ratio | 0.1-0.5 g/(A·min) | Critical process control parameter |
| Shielding gas flow | 8-15 L/min | Ensures adequate protection |
| Nozzle-to-work distance | 5-10 mm | Affects powder delivery efficiency |
The experimental results demonstrate that the dilution ratio can be effectively controlled within the range of 15-40% by adjusting the powder-to-current ratio. For nickel-based alloy cladding (such as Inconel 625) on carbon steel substrates, a dilution ratio below 20% is typically required to maintain the corrosion resistance properties specified by standards such as API 934.
Process Optimization and Quality Control
The study highlights several critical quality factors for coaxial powder feeding TIG cladding:
- Layer uniformity: Achieved through stable powder feeding and consistent arc stability
- Bond strength: Verified through peel tests or shear tests per NB/T 47014 requirements
- Dilution control: Monitored through optical emission spectroscopy or metallographic analysis
- Surface quality: Controlled by travel speed and powder particle size distribution
Engineering Applications and Standards Alignment
For pressure vessel applications governed by GB/T 150 and ASME VIII Div.1, the cladding layer must satisfy specific requirements regarding thickness, composition, and mechanical properties. The coaxial powder feeding TIG method offers particular advantages for:
- Repair of localized corrosion damage on reactor internals
- Application of thin overlay layers (1-3 mm) where electroslag welding is impractical
- Cladding of complex geometries such as tube sheets and channel covers
- Surface hardening of rotating equipment components
The process qualification per NB/T 47014 requires demonstration of consistent dilution control, adequate bond strength, and freedom from defects such as lack of fusion, porosity, and cracking.
Study Insights and Implications
The integration of numerical simulation with experimental validation provides a powerful approach for process optimization in cladding technology. The ability to predict dilution ratios computationally reduces the number of trial welds required during process development, significantly cutting development costs. For engineers involved in bimetal pressure vessel fabrication, this study reinforces the importance of process parameter control in achieving specification-compliant cladding layers. The coaxial powder feeding approach represents a flexible and controllable cladding technology that bridges the gap between manual weld overlay methods and automated high-deposition-rate processes such as electroslag welding.