1. Overview of Thermal Spray Coating
Thermal spray is a surface coating process where melted (or heated) materials are sprayed onto a surface to form a protective or functional layer. It’s widely used in offshore, wind energy, oil & gas, aerospace, and industrial applications for:
- Corrosion resistance
- Wear resistance
- Thermal insulation
- Electrical conductivity/insulation
- Repair & refurbishment of worn parts
2. Types of Thermal Spray Processes
| Process | Temperature Range | Key Features | Common Applications |
|---|
| Flame Spray | ~3,000°C | Low cost, portable | Corrosion protection, repairs |
| Arc Spray | ~4,000°C | High deposition rate, low porosity | Offshore structures, bridges |
| Plasma Spray | Up to ~15,000°C | High-quality, dense coatings | Turbine blades, aerospace |
| HVOF (High-Velocity Oxygen Fuel) | ~3,000°C | Extremely dense, high bond strength | Wear-resistant coatings |
| Cold Spray | Below melting point | No heat distortion, thick coatings | Electronics, sensitive components |
3. Key Materials Used in Thermal Spray
| Material | Properties | Applications |
|---|
| Zinc & Aluminum | Corrosion resistance | Offshore structures, ships |
| WC-Co (Tungsten Carbide-Cobalt) | Extreme wear resistance | Pump shafts, valves |
| Cr2O3 (Chromium Oxide) | Hard, abrasion-resistant | Textile machinery, seals |
| NiCrBSi (Nickel-based alloys) | High temp. resistance | Turbine components |
| Ceramics (Al2O3, ZrO2) | Thermal barrier coatings | Jet engines, power plants |
4. Surface Preparation for Thermal Spray
- Abrasive blasting (SA 2.5 or SA 3) for adhesion
- Cleaning (degreasing to remove oils)
- Roughening (for mechanical bonding)
- Preheating (for some processes to reduce stress)
5. Application Steps
- Substrate Preparation (cleaning, blasting)
- Spraying (adjusting distance, angle, speed)
- Post-Treatment (sealing, machining, polishing)
6. Advantages of Thermal Spray
- ✔ Versatile (metals, ceramics, polymers)
- ✔ No heat distortion (unlike welding)
- ✔ Thick coatings possible (up to several mm)
- ✔ Field-repairable (portable systems available)
7. Limitations & Challenges
- ❌ Porosity (may require sealing)
- ❌ Brittleness (ceramic coatings)
- ❌ Skill-dependent (operator experience matters)
- ❌ Cost (HVOF & plasma spray are expensive)
8. Industry Standards & Inspection
- ISO 2063 (Metallized coatings for corrosion protection)
- ASTM C633 (Adhesion/cohesion strength test)
- ASTM E1920 (Thickness measurement)
- Porosity testing (ASTM B276)
9. Emerging Trends
- 🔹 Cold Spray (for heat-sensitive components)
- 🔹 Hybrid coatings (nanocomposites for better performance)
- 🔹 Robotic thermal spray (precision automation)
- 🔹 AI-based process optimization
10. Where is Thermal Spray Used?
- Oil & Gas: Valve coatings, pipeline corrosion protection
- Aerospace: Turbine blade coatings
- Wind Energy: Repairing turbine shafts & bearings
- Marine: Ship hulls, offshore platforms
- Automotive: Engine components
