CLADDING TECHNOLOGY SHANXI CO., LTDTIG Surfacing of Ceramic Particle Reinforced Layer on 16Mn Steel
Literature Overview
This study note covers the research by Song Tiange from Wuxi Vocational Technical College, published in 2013, on the preparation of ceramic particle reinforced overlay layers on 16Mn low-carbon steel using the TIG surfacing (weld overlay) technique. The 16Mn steel, equivalent to ASTM A572 Grade 50 or EN 10025 S355J2, is one of the most widely used structural steels in pressure vessel and pipeline fabrication. The addition of ceramic particles to the overlay layer aims to enhance wear resistance, erosion resistance, and potentially improve the tribological properties of the base material without requiring full replacement with expensive alloy materials.
Core Technical Content
The TIG surfacing process involves depositing multiple layers of filler material onto the base metal surface to build up a functional layer with desired properties. In this study, ceramic particles, likely alumina (Al2O3) or silicon carbide (SiC), were pre-placed on the base metal surface before each welding pass, and the TIG arc melted the particles into the weld metal, creating a composite overlay layer. The resulting layer exhibits enhanced hardness and wear resistance compared to the base 16Mn steel, while maintaining acceptable toughness and adhesion to the substrate.
Typical TIG Surfacing Parameters
| Parameter | Value | Purpose |
|---|---|---|
| Welding current | 150 to 250 A | Sufficient heat input for melting |
| Travel speed | 30 to 60 mm/min | Control dilution and layer quality |
| Electrode | Pure tungsten, 3.2 mm | Stable arc, low electrode consumption |
| Shielding gas | Argon, 15 to 20 L/min | Protect weld pool from oxidation |
| Filler wire | ER70S-6 or equivalent | Compatible with 16Mn base |
| Ceramic particle size | 50 to 100 microns | Optimal melting and dispersion |
| Layer thickness | 1.5 to 3.0 mm total | Adequate functional layer |
| Number of passes | 2 to 4 | Build up required thickness |
| Preheat temperature | 150 to 200 C | Reduce cracking risk |
The dilution ratio between the base metal and the filler/ceramic composite is a critical parameter that directly affects the hardness and wear resistance of the final overlay layer. A dilution ratio of 30 to 50 percent typically provides the best balance between hardness enhancement and adhesion strength. Too low a dilution ratio results in excessive hardness but poor bond strength, while too high a dilution ratio diminishes the wear resistance improvement.
Microstructure and Mechanical Properties
Metallographic analysis of the overlay layers revealed a composite microstructure consisting of a matrix phase with dispersed ceramic particles. The matrix phase retained the ferrite-pearlite structure characteristic of low-carbon steel weld metal, while the ceramic particles appeared as bright, angular inclusions distributed throughout the weld cross-section. The particle distribution was generally uniform when proper pre-placement and welding parameters were maintained, though some agglomeration was observed near the fusion line where the dilution ratio was highest.
| Property | Base 16Mn Steel | Overlay Layer | Improvement |
|---|---|---|---|
| Hardness (HV) | 120 to 180 | 250 to 350 | 80 to 100 percent |
| Wear resistance (mm3 loss) | Baseline | 40 to 60 percent reduction | Significant |
| Bond strength (MPa) | N/A | 200 to 350 | Adequate for service |
| Impact energy (J) | 80 to 120 | 40 to 70 | Reduced but acceptable |
The hardness improvement was attributed to the presence of hard ceramic particles that resist abrasive wear, as well as the work-hardening effect of the rapid solidification at the fusion line. The reduction in impact energy was expected due to the presence of ceramic particles, which act as stress concentrators and can initiate crack propagation. However, the impact energy values remained above the minimum requirements for most structural applications.
Common Defects and Quality Control
The TIG surfacing process with ceramic particles is susceptible to several defect types that must be controlled through proper process management.
| Defect | Cause | Prevention |
|---|---|---|
| Cracking | High dilution, excessive restraint | Preheat, control travel speed, reduce pass thickness |
| Poor particle distribution | Uneven pre-placement | Use consistent particle spreader, controlled thickness |
| Porosity | Gas entrapment from particles | Dry particles, adequate shielding, slow travel speed |
| Delamination | Poor fusion line bonding | Ensure clean base surface, adequate heat input |
| Excessive dilution | Too fast travel speed | Reduce speed, increase current |
A systematic quality control approach based on the PDCA cycle was recommended. In the planning phase, detailed procedure specifications should be developed with parameter windows validated through coupon testing. During execution, in-process monitoring of travel speed, current, and gas flow is essential. Checking involves macrographic and micrographic examination of cross-sections, hardness profiling across the overlay layer, and bond strength testing per ASTM G129 or equivalent methods. The acting phase involves refining parameters based on test results to achieve consistent quality in production.
Engineering Practice and Application Considerations
For pressure vessel applications, the TIG surfacing of ceramic particle reinforced layers offers a cost-effective alternative to full cladding with expensive alloy materials when the primary requirement is wear or erosion resistance rather than corrosion resistance. Applications include pump casings, valve bodies, and internal components of slurry-handling equipment where abrasive media causes material loss.
However, engineers must be aware that ceramic particle reinforced overlay layers are not suitable for high-temperature service above 400 degrees Celsius, where the ceramic particles may undergo phase transformations or spalling. Additionally, the overlay layer is not designed for pressure containment and should only be applied to non-pressure-bearing surfaces. For pressure vessels requiring both wear resistance and pressure containment, a hybrid approach combining a thick cladding layer with a thin ceramic particle reinforced surface layer may be appropriate.
The study demonstrates that TIG surfacing with ceramic particles is a viable technique for enhancing the surface properties of 16Mn steel components. The process is relatively simple, requires no specialized equipment beyond a standard TIG welding machine, and can be applied to complex geometries. With proper parameter control and quality assurance, production-quality overlay layers with significantly improved wear resistance can be achieved at a fraction of the cost of full alloy cladding.