Wear Resistance and Wear Mechanism of Metal Overlay Containing Inherent Hard Carbide Particles

Literature Overview

The paper by Yang Shanglei and colleagues, published in the Chinese Journal of Tribology in 2004 (Vol. 24, No. 6, pp. 508-511), investigates the wear resistance and wear mechanism of metal overlay layers containing inherently formed hard carbide particles. The study employed arc metallurgical synthesis using ferrotitanium (Fe-Ti), ferrovanadium (Fe-V), graphite, and rutile (TiO2) as alloying components to produce overlay layers containing TiC and VC hard carbide particles. The tribological performance was evaluated using an MLD-10 dynamic load friction and wear tester, while phase composition, microstructure, and worn surface morphology were characterized through X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Core Technical Findings

The research demonstrates that the synthesized overlay layer achieves a mass wear loss per unit area approximately one-ninth (1/9) of that of the conventional EDZCr-C-15 electrode overlay layer, representing a substantial improvement in resistance to abrasive wear. The base matrix of the overlay layer consists of low-carbon martensite, with hard carbide particles dispersed throughout the matrix in a fine and uniform distribution. The combination of the hard carbide particles and the low-carbon martensite matrix produces a synergistic effect of toughness and hardness, which is the fundamental mechanism behind the enhanced wear resistance.

The following table summarizes the key technical parameters and comparative results:

Interpretation of Technical Points

The formation of TiC and VC through in-situ arc metallurgical reactions represents a fundamentally different approach from simply adding pre-made carbide particles to the welding flux or electrode coating. The arc melting environment provides sufficient thermal energy and a reducing atmosphere to promote the chemical reaction between titanium/vanadium and carbon, resulting in carbide particles that are inherently well-bonded to the matrix without the interfacial defects that often plague exogenous particle additions.

The synergistic effect between the hard carbide particles and the low-carbon martensite matrix deserves particular attention. In tribological terms, the hard carbides serve as the primary load-bearing phase that resists material removal through ploughing and micro-cutting mechanisms, while the relatively ductile low-carbon martensite matrix provides the necessary toughness to prevent catastrophic fracture of the carbide network. This is analogous to the composite reinforcement principle in ceramic-metal composites, where the hard phase provides wear resistance and the ductile phase provides damage tolerance.

The choice of rutile (TiO2) as a flux component is also significant from a metallurgical perspective. Rutile flux provides a stable arc, good slag fluidity, and acts as an oxygen scavenger, which helps maintain a reducing atmosphere favorable for carbide formation. The presence of excess titanium in the form of ferrotitanium ensures that sufficient titanium is available for TiC formation while also contributing to the overall hardenability of the matrix.

Engineering Practice Implications

For engineers dealing with wear-critical components in mining, cement, and material handling industries, this research offers a practical pathway to significantly extend service life. Components such as crusher hammers, conveyor rollers, and pump impellers that suffer from severe abrasive wear could potentially benefit from overlay layers incorporating in-situ formed TiC and VC particles. The 1/9 reduction in wear loss translates directly into extended replacement intervals, reduced downtime, and lower total cost of ownership.

However, several practical considerations must be addressed before industrial deployment. The arc metallurgical synthesis process requires careful control of the alloying additions and their proportions to ensure consistent carbide formation. The Fe-Ti and Fe-V additions increase material costs compared to conventional Cr-C overlays, and the process requires more sophisticated equipment than standard SMAW or FCAW overlay welding. Additionally, the weldability of the resulting overlay layer on thick-section base metals may require careful preheating and interpass temperature control to avoid excessive residual stress and cracking.

Key Questions and Reflections

One question that arises from this study is the long-term stability of the TiC and VC particles under sustained abrasive loading. While the initial wear resistance improvement is dramatic, it remains to be determined whether the carbide particles undergo fragmentation, pullout, or dissolution under prolonged sliding contact. Another important consideration is the transition from mild to severe wear regimes. The study focuses on abrasive wear under dynamic loading, but in practical applications, components may experience a combination of abrasive, adhesive, and erosive wear mechanisms, which could alter the relative contribution of the carbide particles to overall wear resistance.

Furthermore, the study does not extensively address the residual stress state of the overlay layer. In-situ carbide formation involves significant volume changes as metallic Ti and V react with carbon to form carbides, which may generate additional transformation stresses. These stresses, combined with the thermal stresses from the welding process, could influence the crack resistance of the overlay layer in service.

Study Insights and Implications

This research contributes meaningfully to the understanding of in-situ composite overlay technology and provides a viable alternative to conventional hardfacing approaches. The principle of generating hard phases through in-situ reactions within the weld pool is elegant and addresses the fundamental interfacial bonding problem that limits the performance of exogenous particle-reinforced overlays. For the steel pipe and fitting industry, this approach could be particularly relevant for overlaying wear-critical sections of piping systems in slurry transport applications, where the combination of corrosion and abrasion accelerates component degradation. The methodology of using multiple alloying elements to simultaneously control matrix properties and reinforcement phase characteristics represents a design philosophy that can be extended to other overlay systems.