Microstructure and Sliding Wear Performance of High-Chromium Bimetallic Wear-Resistant Plate Overlay Weld Layer

Literature Overview

The study by Liu Tianjun, Li Xintong, and Wang Qingliang from Hebei Iron and Steel Group Mining Co. and China University of Mining and Technology examines the tribological behavior of high-chromium bimetallic wear-resistant plate overlay weld layers under controlled sliding friction conditions. The research systematically evaluates wear performance under varying loads (200 N and 600 N) and environmental conditions (dry friction and quartz sand abrasion), providing comparative data against conventional martensitic wear-resistant steel.

Microstructural Characterization

The overlay weld layer microstructure is dominated by Cr₇C₃ carbide particles dispersed in an α-Fe matrix, with minor amounts of Cr₂₃C₆ carbide present. This phase composition is characteristic of high-chromium cast iron and overlay weld systems where chromium content exceeds approximately 12 wt%.

Feature	Description	Engineering Significance
Primary hard phase	Cr₇C₃ carbide	Primary wear resistance contributor
Secondary hard phase	Cr₂₃C₆ carbide (minor)	Supplementary hardness contribution
Matrix	α-Fe	Ductile binder for carbide network
Hardness gradient	Increases from base steel toward overlay	Indicates progressive dilution reduction

The hardness gradient observed from the base steel toward the overlay layer is a critical feature that reflects the dilution profile during multi-pass overlay welding. This gradient is beneficial from a stress distribution perspective, as the gradual transition reduces the risk of interfacial cracking under thermal cycling.

Wear Performance Analysis

The comparative wear testing reveals that the high-chromium overlay weld layer demonstrates superior sliding wear resistance compared to conventional martensitic wear-resistant steel:

Condition	Friction Coefficient	Mass Loss vs. Martensitic Steel	Volume Wear Rate vs. Martensitic Steel
Dry friction	Same level as martensitic steel	Lower	Lower
Quartz sand abrasion	—	Lower	Lower

The wear mechanism analysis identifies abrasive wear as the dominant mode in both environments. Under dry friction conditions, wear is primarily driven by micro-asperity plowing, where the hard carbide particles resist penetration by the counterface asperities. Under quartz sand conditions, the mechanism combines micro-asperity plowing with hard quartz particle micro-cutting, with both environments exhibiting concurrent fatigue spalling wear.

The fatigue spalling component is particularly significant because it indicates that even with superior abrasive resistance, the overlay layer is subject to subsurface crack initiation and propagation under cyclic contact loading. This finding has direct implications for service life prediction in applications such as conveyor rollers, chute linings, and grinding mill components where cyclic loading is inevitable.

Practical Engineering Considerations

For engineers selecting wear-resistant overlay solutions for mining and material handling applications, this study provides several actionable insights:

The high-chromium overlay offers equal or better friction characteristics than martensitic steel while delivering superior wear resistance, making it a preferred choice for applications where both wear life and controlled friction are important
The 200 N and 600 N load levels tested represent relatively moderate contact pressures; extrapolation to higher-pressure applications (such as mill liners or high-pressure grinding rolls) should be approached with caution
The presence of fatigue spalling wear suggests that periodic inspection for subsurface cracking may be warranted in cyclic loading applications, even when surface wear rates appear acceptable

Study Insights and Process Optimization Recommendations

The study effectively demonstrates that the Cr₇C₃-rich microstructure provides a favorable balance of hardness and toughness for sliding wear applications. However, I would emphasize that the test conditions—specifically the relatively low loads and controlled sliding geometry—do not fully replicate the complex multiaxial stress states encountered in real mining equipment. Impact loading, fretting, and corrosion-abrasion synergy are additional degradation mechanisms that may limit the practical advantage of high-chromium overlays in certain service environments.

From a process perspective, achieving the desired Cr₇C₃-rich microstructure requires careful control of chromium content, carbon equivalent, and cooling rate. The dilution effect from the base steel during overlay welding can shift the microstructure toward more Cr₂₃C₆-rich compositions if dilution is excessive, potentially increasing brittleness. Multi-pass welding with controlled heat input per pass, adequate preheating, and appropriate filler metal selection are essential process parameters for achieving the target microstructure consistently in production environments.