Iron-Based High-Alloy Wear-Resistant Overlay Layer Wear Failure Mechanism Study Note

Literature Overview

This research, published in 2000 by Zhu Jiaqi, He Shi, and Zhang Xiangjun from the Harbin Welding Institute, was funded by the former Ministry of Machine Building (Project 95JA0506). The study investigates the wear failure mechanisms of iron-based high-alloy wear-resistant overlay layers under ambient temperature sliding dry friction conditions. This work is particularly significant for understanding the fundamental wear processes that govern the service life of overlay components in industrial applications.

Test Methodology and Experimental Setup

The wear testing was conducted using a standardized pin-on-disk apparatus under controlled conditions. The experimental parameters were carefully selected to simulate realistic industrial wear scenarios while maintaining reproducibility.

The specimens were prepared by depositing the overlay layers on steel substrates using appropriate welding processes (SAW, SMAW, or GMAW depending on the specific alloy system). The overlay surfaces were ground to a consistent finish (Ra 0.8-1.6 μm) to ensure uniform initial contact conditions.

Wear Failure Mechanisms Identified

The study identified several distinct wear failure mechanisms operating at different stages and under different conditions:

1. Adhesive Wear

• Occurs at low sliding distances and moderate loads
• Mechanism: micro-welding at asperity contacts followed by shear
• Evidence: transferred material on counterface, wear scars with smeared appearance
• Severity: moderate, self-limiting in most cases

2. Abrasive Wear

• Dominant mechanism at higher loads and longer sliding distances
• Mechanism: hard particles or asperities cutting into the softer surface
• Evidence: parallel grooves in sliding direction, material removal in furrows
• Severity: severe, progressive material loss

3. Fatigue Wear (Sub-surface)

• Occurs under cyclic loading conditions
• Mechanism: crack initiation at or below the surface, propagation, and spalling
• Evidence: subsurface cracks, flaked material, Hertzian contact damage
• Severity: catastrophic when spalling occurs

4. Oxidative Wear

• Contributes to overall wear rate under ambient conditions
• Mechanism: oxidation of exposed metal followed by removal of oxide layer
• Evidence: oxide layers on worn surfaces, third-body particles
• Severity: moderate, can be beneficial in some cases (protective oxide formation)

5. Erosive Wear

• Observed in conditions with particle impingement
• Mechanism: momentum transfer from impacting particles causes material removal
• Evidence: dimples, craters, directional material removal
• Severity: depends on particle velocity and impact angle

Microstructural Evolution During Wear

The study examined how the microstructure of the overlay changes during the wear process:

The transition from steady-state to severe wear was found to be influenced by:

• Carbide network formation leading to stress concentration
• Work hardening saturation followed by softening
• Thermal effects from frictional heating
• Environmental interactions (oxidation, contamination)

Quantitative Wear Analysis

The wear rates were quantified using weight loss and volumetric measurements, with results normalized to specific wear rates:

The results demonstrate that increasing the content of high-hardness carbide formers (W, V) significantly improves wear resistance. The optimal composition balances carbide volume fraction with matrix toughness to prevent premature fatigue failure.

Engineering Practice and Design Guidelines

Based on the wear failure mechanisms identified, the following design guidelines are recommended for engineering applications:

1. Match overlay hardness to counterface: The overlay should be harder than the counterface to minimize adhesive and abrasive wear, but not excessively hard to avoid brittle fracture.
2. Control carbide distribution: Avoid network carbides that create crack initiation sites; prefer dispersed carbides for uniform wear protection.
3. Consider operating conditions: High-speed applications may benefit from tougher overlays with lower carbide volume fraction, while low-speed abrasive applications favor maximum hardness.
4. Implement proper welding procedures: Minimize defects (porosity, lack of fusion) that can initiate wear failure; ensure adequate bonding strength.
5. Monitor service performance: Regular inspection of worn components can identify approaching failure and enable preventive maintenance.

Study Insights and Conclusions

This research provides a comprehensive understanding of the wear failure mechanisms in iron-based high-alloy overlay layers, which is essential for rational design and selection of overlay systems. The identification of multiple interacting wear mechanisms highlights the complexity of tribological behavior and the importance of considering the complete operating environment in overlay design.

The practical significance of this work extends to maintenance planning and component life prediction. By understanding the transition from steady-state to severe wear, engineers can establish inspection intervals and replacement criteria that optimize component utilization while preventing catastrophic failure. The research also provides a foundation for developing improved overlay compositions through targeted alloy design that addresses specific wear failure modes. This study remains a valuable reference for tribologists and welding engineers working on wear-resistant surfacing applications.