Bimetallic vs Nitrided Screw Barrels: How to Compare Wear Resistance

Surface Treatment Options for Screw Barrels

The surface treatment of a screw barrel determines its wear resistance, corrosion resistance, and ultimately its service life. Two dominant technologies compete in the market: nitriding (gas or ion) and bimetallic centrifugal casting. Understanding their differences helps manufacturers make cost-effective decisions.

Nitrided Screw Barrels (38CrMoAlA)

Nitriding creates a hard surface layer (900-1100 HV) on 38CrMoAlA alloy steel through nitrogen diffusion at 500-550°C. The hardened layer typically reaches 0.4-0.7mm depth.

Advantages

• Lower initial cost (40-60% less than bimetallic)
• Suitable for non-abrasive materials (PE, PP, PS, ABS)
• Good dimensional stability during treatment
• Easier to re-nitride after wear

Limitations

• Thin hardened layer wears through faster with abrasive fillers
• Limited corrosion resistance against chlorine-based materials
• Typical service life: 1-3 years depending on material processed

Bimetallic Screw Barrels

Bimetallic barrels feature a centrifugally cast alloy lining (typically iron-boron or nickel-based alloys) with hardness reaching 58-65 HRC. The lining thickness is 2-5mm.

Advantages

• Superior wear resistance for glass fiber, calcium carbonate, and mineral fillers
• Excellent corrosion resistance for PVC and fluoropolymers
• Service life 3-5x longer than nitrided barrels in abrasive conditions
• Maintains consistent bore diameter over time

Limitations

• Higher upfront investment
• Cannot be re-lined economically after wear-through
• Longer lead time for manufacturing

Cost-Benefit Analysis

For operations processing unfilled polyolefins at moderate volumes, nitrided barrels offer the best value. However, any operation involving glass fiber content above 15%, mineral fillers, or corrosive PVC compounds should invest in bimetallic barrels. The 3-5x longer service life typically delivers a lower total cost of ownership despite the higher purchase price.

Nanhaiya Solutions

Nanhaiya manufactures both nitrided and bimetallic screw barrels, and also offers alloy spray welding as a middle-ground option. Our technical team provides material analysis and lifecycle cost projections to help you choose the most economical solution for your specific application.