CLADDING TECHNOLOGY SHANXI CO., LTDMicrostructure and Sliding Friction Wear Performance of High-Chromium Bimetal Wear-Resistant Plate Overlay Layers
Literature Overview
This paper, authored by Liu Tianjun, Li Xintong, and Wang Qingliang from Hebei Iron and Steel Group Mining Co., Ltd. and China University of Mining and Technology, investigates the microstructural characteristics and sliding friction wear performance of high-chromium bimetal wear-resistant plates. The research was funded by the Central Universities Basic Scientific Research Business Fee Special Fund (2019XKQYMS38). Published in 2026 in the field of mechanical engineering materials, this study addresses the practical needs of the mining and bulk material handling industries for high-performance wear-resistant materials.
Core Technical Analysis
Microstructural Characteristics of High-Chromium Overlay Layers
High-chromium cast iron overlay layers typically contain 12-30 wt% Cr, with the chromium content directly influencing the type, morphology, and volume fraction of carbide phases formed. The microstructural features of these overlay layers are critical for determining their wear resistance:
| Microstructural Feature | Typical Composition | Hardness (HV) | Wear Resistance Contribution |
|---|---|---|---|
| Cr7C3 carbides | Cr7C3 | 1800-2000 | High resistance to abrasive wear |
| Cr23C6 carbides | Cr23C6 | 1400-1600 | Moderate resistance to abrasive wear |
| Martensite matrix | Fe-Cr-Mn | 400-600 | Provides toughness and crack resistance |
| Residual austenite | Fe-Cr-Ni (if Ni added) | 200-300 | Contributes to toughness |
| Primary carbides | Cr7C3 (coarse) | 1800-2000 | Can act as crack initiation sites if too large |
The transition from Cr7C3 to Cr23C6 carbides occurs at approximately 20-22 wt% Cr, and this transition has significant implications for wear resistance. Cr7C3 carbides are harder and more wear-resistant but more brittle, while Cr23C6 carbides are slightly softer but more fracture-resistant. The optimal chromium content for a given application depends on the specific wear mechanism and loading conditions.
Sliding Friction Wear Behavior
The sliding friction wear performance of high-chromium overlay layers is characterized by the following mechanisms:
- Abrasive wear: Dominant mechanism in most mining applications, where hard particles embedded in the material stream plow and cut the overlay surface. The hardness and morphology of carbide phases are the primary factors controlling abrasive wear resistance.
- Adhesive wear: Occurs when material transfer between the overlay surface and the counterface takes place during sliding contact. The presence of hard carbide phases can reduce adhesive wear by limiting the area of intimate contact.
- Oxidative wear: At elevated temperatures, oxidation of the overlay surface can contribute to material loss. The chromium content influences the formation of protective oxide layers.
- Fatigue wear: Cyclic loading during sliding can initiate subsurface cracks that propagate to the surface, leading to material spalling. The matrix toughness is critical for resisting fatigue wear.
Effect of Overlay Layer Composition on Wear Performance
The composition of the high-chromium overlay layer can be adjusted to optimize wear resistance for specific service conditions:
| Alloying Element | Typical Range (wt%) | Effect on Microstructure | Effect on Wear Resistance |
|---|---|---|---|
| Cr | 12-30 | Controls carbide type and volume fraction | Primary wear resistance contributor |
| C | 2.5-4.0 | Promotes carbide formation | Increases carbide volume fraction |
| Mo | 2-5 | Stabilizes Cr7C3 carbides | Improves high-temperature wear resistance |
| Mn | 1-3 | Affects austenite stability | Moderate effect on wear resistance |
| Ni | 0-5 | Stabilizes austenite | Improves toughness |
| Si | 1-2 | Deoxidizer, affects matrix | Minor effect on wear resistance |
| V | 0-2 | Forms hard vanadium carbides | Improves abrasive wear resistance |
Engineering Practice Integration
High-chromium bimetal wear-resistant plates are widely used in mining equipment, including conveyor rollers, chutes, hoppers, crusher liners, and excavator bucket teeth. The bimetal construction combines a tough steel backing with a hard, wear-resistant high-chromium overlay layer, providing both structural integrity and surface durability.
From a manufacturing perspective, the key considerations for producing high-quality high-chromium bimetal plates include:
- Ensuring adequate bond strength between the overlay layer and the steel backing, which is critical for preventing delamination during service.
- Controlling the cooling rate to achieve the desired microstructure, particularly the size and distribution of carbide phases.
- Maintaining uniform overlay layer thickness across the plate surface to ensure consistent wear performance.
- Implementing proper heat treatment procedures to optimize the balance between hardness and toughness.
The welding process used for depositing the high-chromium overlay layer is typically submerged arc welding (SAW) or flux-cored arc welding (FCAW), with the choice depending on the required layer thickness and production volume. The welding consumables are specifically formulated to achieve the desired overlay composition and microstructure.
Key Questions and Reflections
The study raises important questions regarding the relationship between microstructure and wear performance in high-chromium overlay layers. While it is well established that harder carbide phases provide better abrasive wear resistance, the optimal balance between hardness and toughness is application-specific. In mining applications, where the overlay layer is subjected to both abrasive and impact loading, excessive hardness can lead to brittle fracture and premature failure.
Another important consideration is the effect of the overlay layer thickness on wear performance. Thicker overlay layers provide longer service life but may be more susceptible to cracking due to higher residual stresses and greater thermal expansion mismatch with the backing. The optimal overlay thickness must be determined by balancing service life requirements with the risk of overlay failure.
Study Insights and Implications
The research by Liu Tianjun and colleagues provides valuable insights into the microstructure-property relationships in high-chromium bimetal wear-resistant plates. The detailed characterization of carbide phases and their influence on sliding friction wear performance offers practical guidance for the design and selection of high-chromium overlay systems for mining applications.
For engineers specifying high-chromium bimetal wear-resistant plates, the key insight is that the optimal composition and microstructure depend on the specific service conditions. A systematic approach to material selection, based on a thorough understanding of the wear mechanisms and loading conditions, is essential for achieving satisfactory service performance.