How to Repair Worn Barrels and Screws?
For worn barrels and screws, the core repair strategy centers on "resurfacing the screw, reconditioning the barrel bore."
Regarding the screw: minor wear can be addressed through grinding; for severe wear, the preferred methods are thermal spraying with wear-resistant alloys or hardfacing, followed by grinding.
Regarding the barrel: the standard approach involves boring and grinding the inner bore, followed by fitting a new screw, or installing an alloy steel liner. As a maintenance professional who frequently deals with wear-related issues, I advise you to prioritize evaluating the cost-to-service-life ratio of any repair solution. Do not attempt to save a small amount of money by choosing a repair method with an extremely short lifespan, as this will inevitably lead to frequent downtime.
Screw Repair Solutions: A Graded Approach Based on Severity
The screw is a consumable component; its repair focuses primarily on restoring its outer diameter and surface hardness. The specific process chosen must be tailored to the degree of wear:
Minor Wear (Scratches, Surface Roughness)
Treatment Method Manual polishing and smoothing using an oilstone or fine emery cloth.
Applicable Scenarios:The surface exhibits only minor scratches; the screw's geometric dimensions remain unchanged, and the fit clearance is unaffected.
Advantages: Extremely low cost; can be performed on-site without the need to disassemble and ship the component out for repair.
Moderate Wear (Reduced Diameter, Thinned Flights)
Treatment Method:Thermal spraying with wear-resistant alloys. The screw surface is pre-treated, a layer of wear-resistant alloy is applied (a relatively low-cost process), and the component is then ground to restore its standard dimensions.
Applicable Scenarios: The screw diameter has diminished, but the base material retains sufficient structural integrity; the goal is to restore dimensions and enhance wear resistance. This currently represents the most cost-effective professional repair method available.
Note:This procedure must be performed by a specialized thermal spraying facility to ensure proper coating adhesion.
Severe Wear (Deep Grooves, Significant Dimensional Deviations)
Treatment Method A (Hardfacing): A layer of wear-resistant alloy (containing elements such as C, Cr, V, Co, W, B, etc.), 1–2 mm in thickness, is deposited onto the screw flights via hardfacing, followed by grinding to restore the correct dimensions. This method offers exceptional resistance to both wear and corrosion; however, due to its high cost, it is typically reserved for screws with specialized requirements.
Treatment Method B (Hard Chrome Plating): A layer of hard chrome is applied to the surface. While chrome provides excellent resistance to wear and corrosion, the hard chrome layer is prone to peeling-a significant risk that necessitates careful consideration when selecting this option.
Treatment Method C (Remanufacturing): If the screw has fractured or is so severely worn that the cost of repair exceeds that of a new component, a new screw should be manufactured directly, sized to match the actual inner diameter of the barrel.
