EV Lightweight Structural Parts: Barrel Coating Technologies for Carbon Fiber Abrasion

As range requirements for Electric Vehicles (EV) continue to rise, "Replacing Steel with Plastic" has become a core industry trend. Carbon Fiber Reinforced Thermoplastics (CFRTP), with their exceptional specific strength and modulus, are the preferred materials for battery trays, seat frames, and body structural components. However, the extreme hardness of carbon fiber poses a massive abrasive challenge to the twin screw extruder barrels and screws.

When producing high-fill (30%-50%) carbon fiber modified plastics, the risk of equipment failure far exceeds that of standard glass fiber:

• High-Hardness Erosion: Carbon fibers break during the shearing process; the resulting fragments possess needle-like hardness that quickly strips the protective layer off standard nitrided steel barrels.
• Fiber Bridging and High Pressure: Carbon fibers tend to form network structures, increasing melt viscosity. This leads to higher radial pressure on the inner barrel wall, accelerating physical wear.
• Interface Peeling: High-velocity fiber particles cause "micro-cutting" on metal surfaces, expanding the barrel's internal diameter and destroying clearance accuracy.

For the rigorous conditions of EV structural parts, traditional single-metal barrels are no longer sufficient. Advanced coating or liner technologies must be introduced.

• Recommended Solution: Utilize bimetallic barrels with liners containing high tungsten carbide content.
• Hardness Standard: The liner hardness should reach 60 - 64 HRC. This is sufficient to resist the cutting action of carbon fiber fragments.
• Technical Advantage: The centrifugal casting process ensures a high-strength bond between the liner and the substrate. A thickness of 2.0 mm - 3.0 mm provides an exceptionally long service life.

• Material Advice: Screw elements should be made from high-vanadium powder metallurgy steel (such as the CPM series) and paired with PVD (Physical Vapor Deposition) coatings.
• Clearance Precision: Unilateral clearance must be precisely controlled within 0.05 mm - 0.08 mm. Precise clearance reduces the residence time of material in the gaps, slowing down the wear rate. (Reference: Material Wear Comparison Report - Ref: #QC-2024-EXP-08)

Beyond hardware materials, system stability directly affects the performance retention of carbon fiber:

• Low-Shear Temp Control: Optimize screw configurations to reduce over-shearing and keep temperature fluctuations within +/- 1°C. This prevents polymer degradation that causes poor fiber wetting.
• Wear Warning Mechanism: It is recommended to inspect the barrel internal diameter every 500 tons of output. If wear exceeds 0.10 mm, promptly adjust the process or replace the liner to ensure mechanical consistency of the structural parts.

In the EV supply chain, high-quality modified plastics depend on stable extrusion processes. Selecting high-precision screws and barrels with ultra-hard coatings (>60 HRC) and mirror polishing (Ra < 0.4 um) not only extends equipment life by more than three times but is also a prerequisite for ensuring carbon fiber structural parts meet safety standards. For leading global compounders, wear-resistant systems compatible with Coperion or JSW standards have become the industry baseline.