Extending Screw Life in High-Wear Applications — A Comparison of Coating Solutions
Processing abrasive or filled polymers such as wood-plastic composites (WPC), glass fiber reinforced plastics (GFRP), and CaCO₃-filled compounds puts extreme wear stress on extrusion screws.
Without adequate protection, screw flight wear accelerates, leading to:
- Decreased output and pressure
- Poor melt quality
- Frequent downtime for replacement
To maximize screw longevity, surface coating technologies offer powerful protection. Let’s compare the main options to help you select the best fit.
1. Nitriding
Process:
Diffusion of nitrogen atoms into steel surface to create a hard, wear-resistant layer.
Advantages:
- Cost-effective
- Hardness up to 60 HRC
- Improved corrosion resistance
Limitations:
- Layer thickness only ~0.3 mm
- Not ideal for highly abrasive fillers
- Surface can wear through over time
Best For:
Virgin polymers, mild abrasives, and general-purpose extrusion.
2. Tungsten Carbide Coating (HVOF Spray)
Process:
High-Velocity Oxygen Fuel spraying deposits tungsten carbide particles in a metal matrix coating.
Advantages:
- Extremely high hardness (68–72 HRC)
- Excellent abrasion and impact resistance
- Coating thickness 0.5–1 mm
Limitations:
- Higher cost
- Requires precise application to avoid cracking
- Repair more complicated
Best For:
WPC, glass fiber reinforced plastics, heavy CaCO₃ filled materials.
3. Bimetallic Screws (Centrifugal Casting)
Process:
Wear-resistant alloy layer cast directly onto screw substrate.
Advantages:
- Thick, uniform hard layer
- Excellent wear and corrosion resistance
- Longest lifespan
Limitations:
- High initial cost
- Requires specialized machining
Best For:
Extreme wear environments, recycled materials, long production runs.
4. Chrome Plating
Process:
Electroplating hard chrome onto screw surface.
Advantages:
- Moderate hardness (~60 HRC)
- Good corrosion resistance
Limitations:
- Coating adhesion issues under heavy abrasion
- Environmental concerns with chromium use
Best For:
Moderate wear and corrosion protection.
Summary Table
| Coating Type | Hardness (HRC) | Thickness (mm) | Cost Level | Best Application |
|---|---|---|---|---|
| Nitriding | ~60 | 0.3 | Low | Virgin polymers, mild abrasives |
| Tungsten Carbide | 68–72 | 0.5–1.0 | High | High abrasives, WPC, GF composites |
| Bimetallic Casting | 62–70 | 1.0+ | Highest | Extreme wear, recycled compounds |
| Chrome Plating | ~60 | 0.05–0.1 | Medium | Moderate wear and corrosion |
Practical Tips from Juyuan
- Match coating type to your polymer and filler abrasiveness
- Monitor screw wear with regular inspections
- Combine coatings with optimized screw geometry for best results
- Consider lifecycle cost, not just upfront price
Contact Zhoushan Juyuan for Custom Coating Solutions
We provide expert advice and customized screw coatings tailored to your material and production needs.
Zhoushan Juyuan Machinery Co., Ltd.
📧 Email: cxj.job@gmail.com
📱 WhatsApp: +86 13905808474
🌐 Website: https://juyuan-machinery.com