CLADDING TECHNOLOGY SHANXI CO., LTDMicrostructure and Property Analysis of Wear-Resistant Alloy Cladding on Intensive Mixer Rotors
Literature Overview
This 2022 publication by Wang Xin from Dalian Rubber & Plastic Machinery Co., Ltd. was published in Rubber and Plastic Technology and Equipment (橡塑技术与装备). The paper focuses on the application of weld overlay cladding of wear-resistant alloys on the rotors of intensive mixers used in rubber and plastic processing. Intensive mixers are critical equipment in the rubber industry, and their rotors undergo severe abrasive and adhesive wear from raw rubber compounds, fillers, and reinforcing agents. The study provides a systematic analysis of the microstructure and mechanical properties of the cladding layer.
Core Technical Content
The intensive mixer rotor operates under conditions of high torque, high temperature (up to 150–200 °C), and continuous contact with abrasive rubber compounds containing silica, carbon black, and other fillers. The base rotor material is typically a ductile cast iron or low-alloy steel, which is insufficient for long-term wear resistance. The cladding layer is designed to provide a hard, wear-resistant surface while maintaining the structural integrity of the rotor.
Cladding Material and Process Selection
| Item | Specification |
|---|---|
| Base material | QT500-7 or 42CrMo |
| Cladding alloy | High-chromium cast iron / Stellite-type / Carbide-reinforced |
| Welding method | GMAW or SAW overlay |
| Filler wire | High-Cr-Mo-V or Co-Cr-W alloy |
| Shielding gas | Ar / CO2 mixture or pure Ar |
| Overlay thickness | 4–10 mm |
| Post-weld treatment | Normalizing or stress relief |
Microstructure Analysis
The authors conducted detailed metallographic examination of the cladding layer and the transition zone. The overlay layer typically consists of a martensitic matrix with dispersed carbides (Cr7C3, Mo2C, VC). The carbide distribution and morphology are critical for wear resistance. In the transition zone, a dilution gradient exists where the base metal elements diffuse into the overlay, forming a mixed microstructure. The degree of dilution affects the hardness and toughness of the transition region.
The paper reports that the cladding layer hardness reaches 55–65 HRC, significantly higher than the base material hardness of 200–280 HBW. The wear resistance improvement is quantified through laboratory abrasion tests, showing a 3–5 times improvement over the uncladded rotor surface.
Engineering Practice Considerations
In rubber processing, the mixer rotor is subjected to a combination of abrasive wear from fillers and adhesive wear from molten rubber compounds. The cladding layer must resist both mechanisms. The authors note that the thermal stability of the overlay is important because the rotor surface temperature can reach 200 °C during operation, which may cause tempering of the martensitic structure. Therefore, the selection of alloying elements that stabilize carbides at elevated temperatures is crucial.
Key Design Parameters
| Parameter | Recommended Value | Rationale |
|---|---|---|
| Overlay hardness | 55–65 HRC | Balance wear resistance and toughness |
| Dilution rate | < 20% | Maintain overlay composition |
| Transition zone width | 1–3 mm | Minimize dilution effects |
| Surface roughness | Ra ≤ 6.3 μm | Reduce adhesive wear |
| Residual stress | Compressive preferred | Improve fatigue life |
Defect Prevention
The paper identifies several common defects in the cladding process:
- Cracking: Caused by high carbon equivalent of the base material and insufficient preheat. Countermeasure: preheat to 150–250 °C and use low-hydrogen filler metal.
- Porosity: Resulting from inadequate shielding or contamination of the base surface. Countermeasure: ensure proper gas flow and surface preparation.
- Undercut and lack of fusion: Due to improper welding parameters. Countermeasure: optimize current, voltage, and travel speed.
Study Reflections
This paper is particularly useful for engineers working in the rubber and plastic processing equipment sector. The authors provide practical guidance on the selection of cladding materials and process parameters that are directly applicable to intensive mixer rotor refurbishment. One important insight is that the microstructure of the transition zone must be carefully controlled, as it is the primary location of failure initiation. The study also highlights the importance of post-weld heat treatment to relieve residual stresses and stabilize the microstructure. Engineers should note that the cladding layer composition and the base metal composition must be compatible to avoid excessive dilution and cracking. The paper serves as a good reference for process development and quality control in this specific application.