Plasma Transferred Arc (PTA) Hardfacing Prepress CAM Vector Guide
Master PTA cladding calculations, dilution control, and multi-pass weave CAM vector planning.
1. Plasma Transferred Arc (PTA) Cladding Technology
Plasma Transferred Arc (PTA) is a high-energy thermal surfacing process used to deposit thick ($1.5 - 6.0\text{ mm}$), wear-resistant, and corrosion-resistant alloy overlays. The constricted arc creates a high-density thermal column ($T > 15,000\text{ K}$) that melts injected powder consumables with minimal substrate melting.
2. Low Dilution & Hardness Preservation
Standard arc welding processes mix 20–35% substrate iron into the deposit, reducing hardness and corrosion resistance. PTA maintains dilution below 5–8%, allowing single-pass deposition of Cobalt Stellite 6 ($42\text{ HRC}$) and Nickel Colmonoy 6 ($60\text{ HRC}$) without multi-layer buffer passes:
HI_{net} = \eta_{thermal} \cdot \frac{V \cdot I}{v_{travel}} \quad (\eta_{thermal} \approx 0.60 - 0.70)
3. Hardfacing Consumable Alloy Matrix
| Alloy Type | Hardness | Matrix Composition | Wear Mechanism | Target Component |
|---|---|---|---|---|
| Stellite 6 (Co-Base) | 40 - 45 HRC | Co-Cr-W-C | High-Temp Metal-on-Metal Galling | Steam / Petrochemical Valve Seats |
| Colmonoy 6 (Ni-Base) | 58 - 62 HRC | Ni-Cr-B-Si | Severe Abrasive Slurry & Acid | Extruder Screws / Decanter Bowls |
| Tungsten Carbide (WC/Ni) | 65 - 70 HRC | 60% WC in NiBSi Matrix | Extreme Gouging / Earth Abrasion | Mining Teeth / Drill Stabilizers |
| Stainless 316L / 625 | 220 HV / 260 HV | Fe-Cr-Ni-Mo / Ni-Cr-Mo | Marine Pitting & Chloride Stress | Subsea Riser Cladding |
4. Prepress CAM Vector Rules for PTA Oscillation Weave
- Trapezoidal Weave Dwell: Program $0.15 - 0.35\text{ sec}$ dwell at weave edges to prevent undercutting and ensure uniform bead flat-top profiles.
- Stepover Overlap Pitch: Adjacent passes should overlap by $25\% - 35\%$ of bead width to eliminate inter-pass valleys.
- SpotItLive Vector Studio Support: Converts CAD profiles into continuous serpentine raster and cylindrical rotary spiral DXF/G-code toolpaths for multi-axis CNC cladding cells and robotic positioning arms.
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