A New Standard in Wear And Corrosion Resistance for Dual-Alloy Screw Barrels: Tungsten Carbide Technology

One

Basic Composition and Function of Screw and Barrel
The screw and barrel are the core plasticizing components of injection molding machines and extruders, hailed as the "heart" of molding equipment. Their primary function is to achieve plastic conveying, melting, and mixing through the rotation of the screw, while establishing pressure within the barrel to ensure uniform plasticization and stable extrusion of the material. Specifically, the barrel serves as the chamber housing the screw, responsible for providing precise heating and cooling control; the screw, through meticulous geometric design—including pitch, L/D ratio, and compression ratio—sequentially performs the three key functions of solids conveying, melting plasticization, and melt metering. The precise coordination between the two ultimately determines plasticizing quality and molding efficiency.

Two

During the operation of screw and barrel, the biggest challenges encountered are wear and corrosion, which are also critical factors directly impacting their service life. Therefore, wear resistance and corrosion resistance are the primary issues that screw and barrel technology must address. The advancement in tungsten carbide technology by suzhou Jwellmech is precisely the core driving force that enables twin-screw and barrel to achieve a leap in wear and corrosion resistance.

1 Material Upgrade: A Qualitative Leap from "Tungsten-Containing" to "High-Content Tungsten Carbide"

The significant improvement in the wear and corrosion resistance of bimetallic screw and barrel sets firstly stems from a fundamental innovation in alloy materials. Traditional alloys contained only about 10% tungsten, relying mainly on the solid solution strengthening effect of tungsten to provide limited wear resistance, which struggled to meet the demanding conditions of highly filled materials. Today, the tungsten carbide content in the alloy from suzhou Jwellmech has been increased to 30% or even 50%, achieving a surge in the concentration of the hard phase. As a ceramic phase with a hardness exceeding HV2000, tungsten carbide forms a rigid "skeleton" structure within the alloy—the higher the content, the stronger the resistance to abrasive wear. This makes it particularly suitable for processing scenarios involving highly filled and high-wear materials such as nylon-reinforced glass fiber, magnetic powders, and aluminum-magnesium powders. Concurrently, tungsten carbide itself is chemically stable. Coupled with the optimized design of the WPT series alloys, a breakthrough in corrosion resistance has been achieved: the WPT1 corrosion-resistant alloy effectively blocks strong corrosive gases like HCl produced during PVC decomposition; the WPT3 composite alloy combines both wear and corrosion resistance, ensuring the substrate remains uneroded under complex operating conditions.

2 Process Innovation: The Densification Revolution Brought by HP/HVOF Thermal Spray Technology

The realization of material properties relies heavily on the support of advanced processes. Previous PTA (Plasma Transferred Arc) welding technology had significant limitations: it could only perform localized spray welding on the screw flight tips, resulting in thick bonding layers, high dilution rates, and a tendency to generate porosity, while failing to cover the screw root—an area prone to corrosion. The introduction of the new generation HP/HVOF (High Pressure High Velocity Oxygen Fuel) thermal spray technology has effectively transformed this situation. This technology propels tungsten carbide powder onto the screw surface at supersonic speeds, creating ultra-high mechanical and metallurgical bonding strength between the coating and the substrate, completely eliminating the risk of coating spalling. The porosity of HVOF coatings is extremely low (typically less than 1%), effectively blocking the infiltration of corrosive media—a key factor in achieving corrosion resistance. More importantly, this technology achieves "comprehensive alloy cladding"—the screw flight tips, flanks, and roots are all uniformly covered by the alloy layer. This resolves the traditional process pain point where the screw root lacked protection and corroded first, thereby multiplying the overall service life of the screw.

3 Structural and Precision Synergy for Reliability

In addition to materials and processes, precision structural design and machining capabilities of suzhou Jwellmech provide the final line of defense for the reliability of bimetallic screw and barrel sets. The base material, made of high-quality 45# or 40Cr steel, undergoes a centrifugal casting bimetallic process to achieve deep metallurgical bonding between the high-hardness alloy layer and the tough substrate—the substrate provides bending toughness to withstand flexural loads, while the alloy layer endows the surface with superior wear and corrosion resistance. The enhancement of precision machining capabilities is equally critical: the machinable length has been extended from 3000mm to 4000mm, with straightness strictly controlled within 0.015mm/m, ensuring that long screws operate without scraping risks during high-speed rotation and effectively protecting the surface tungsten carbide coating from additional mechanical damage. Furthermore, the substrate undergoes nitriding treatment to a depth of 0.5-0.8mm, achieving a hardness of HV960 or above, forming a second hardness barrier beneath the tungsten carbide coating. Even if minimal wear occurs on the surface tungsten carbide layer under extreme operating conditions, the exposed high-hardness nitrided layer provides reliable protection, preventing rapid substrate failure and achieving multi-layered protection from the surface inward.

In Summary: As the core plasticizing components of injection molding machines and extruders, the wear and corrosion resistance of screw and barrel sets directly impact their service life. suzhou Jwellmech has achieved three major breakthroughs through tungsten carbide technology upgrades: In terms of materials, the tungsten carbide content has been increased from 10% to 30%-50%, forming a rigid "skeleton" that significantly enhances wear resistance, while with WPT series alloys effectively resists corrosion such as from HCl. In terms of process, HP/HVOF thermal spray technology replaces traditional PTA, achieving comprehensive alloy cladding on flight tips, flanks, and roots, with high coating bonding strength and extremely low porosity. In terms of structure, the substrate undergoes centrifugal casting and nitriding treatment, with machinable length extended to 4000mm and straightness reaching 0.015mm/m, forming multi-layered protection from surface to interior, thereby multiplying the overall service life of the screw.