Wear Resistance of Ni60-Cr3C2-WC-TiC Plasma Cladding Layer

Overview and Background

Abrasive wear remains one of the most significant failure modes in industrial equipment, particularly in mining, cement, power generation, and material handling applications. Hardfacing and cladding technologies are widely employed to extend the service life of wear-critical components. Plasma transferred arc (PTA) cladding offers distinct advantages over conventional arc welding methods, including lower dilution rates, precise control of layer composition, and the ability to deposit complex carbide-reinforced microstructures. This study from the North University of China investigates the wear resistance characteristics of a Ni60-based cladding layer reinforced with Cr3C2, WC, and TiC carbide particles, deposited via PTA technology. The research provides valuable insights into the synergistic effects of multiple carbide reinforcements on tribological performance.

Microstructural Analysis and Mechanisms

The Ni60 alloy, a nickel-based solid solution alloy containing approximately 6 percent carbon, is known for its excellent combination of wear resistance, corrosion resistance, and toughness. However, the matrix alone may not provide sufficient resistance against severe abrasive conditions. The addition of Cr3C2, WC, and TiC carbides introduces hard phases that resist abrasive material removal through different mechanisms. Cr3C2 (molar hardness approximately 22 GPa) provides a continuous network of hard particles that impede dislocation motion and resist micro-cutting. WC (molar hardness approximately 28 GPa) offers the highest hardness among the three carbides and is effective against sliding abrasion. TiC (molar hardness approximately 24 GPa) contributes to thermal stability and prevents carbide degradation at elevated temperatures.

Carbide Properties and Wear Mechanisms

The researchers found that the PTA process maintained a dilution rate of approximately 10 to 15 percent with the steel substrate, which is significantly lower than the 30 to 50 percent dilution typical of conventional submerged arc or gas metal arc hardfacing. This low dilution is critical because it preserves the intended carbide content and composition of the cladding layer. The microstructural examination revealed that the carbide particles were distributed relatively uniformly throughout the cladding layer, with a particle size range of 2 to 15 micrometers depending on the feed powder composition. The Ni60 matrix exhibited a dendritic microstructure with carbide particles preferentially located at dendrite boundaries and within the interdendritic regions.

Wear Testing Results

The researchers conducted pin-on-disk and dry sand rubber wheel abrasion tests to evaluate the wear resistance of the Ni60-Cr3C2-WC-TiC cladding layer under different loading conditions. The results demonstrated a significant improvement in wear resistance compared to the unalloyed Ni60 cladding layer and conventional high-chromium cast iron overlays. Under moderate loading conditions (50 N normal force), the multi-carbide reinforced cladding layer exhibited a wear rate that was approximately 40 to 60 percent lower than that of the unalloyed Ni60 layer. Under severe loading conditions (100 N normal force), the advantage was more pronounced, with wear rates reduced by 55 to 70 percent relative to the baseline Ni60 layer.

Comparative Wear Performance

The tribological analysis revealed that the wear mechanism transitioned from abrasive wear-dominated at lower loads to a mixed mechanism of abrasive and adhesive wear at higher loads. The multi-carbide reinforcement was particularly effective in suppressing adhesive transfer because the hard carbide particles created a roughened wear surface that disrupted the formation of adhesive junctions. Additionally, the presence of multiple carbide types provided a self-sharpening effect during the wear process; as softer matrix material was removed, harder carbide particles were exposed, maintaining a consistently high surface hardness throughout the wear life.

Process Optimization and Engineering Considerations

The PTA cladding process parameters were optimized to achieve the desired microstructure and wear performance. The researchers identified a current range of 200 to 280 amperes, a voltage range of 22 to 28 volts, and a travel speed of 200 to 400 mm/min as the effective process window for depositing the multi-carbide reinforced layer. The powder feed rate was maintained at 150 to 250 g/min, and an inert gas shielding (argon) flow rate of 15 to 25 L/min was used to prevent oxidation of the molten pool. The substrate preheating temperature was controlled at 150 to 250°C to minimize thermal cracking in the dilution zone.

Optimal PTA Process Parameters

From an engineering practice standpoint, the study highlights several important considerations. First, the cost of WC powder is significantly higher than Cr3C2 or TiC, and the optimal ratio of the three carbides should be determined based on the specific wear environment and economic constraints. Second, the PTA process requires specialized equipment and skilled operators, which may limit its applicability in field repair scenarios. Third, the cladding layer thickness should be designed with adequate allowance for post-deposition machining, typically 1.5 to 3 mm of build-up above the final dimension.

Study Insights and Reflections

This research contributes meaningfully to the understanding of multi-carbide reinforcement strategies in nickel-based PTA cladding alloys. The synergistic effect of combining Cr3C2, WC, and TiC is particularly noteworthy, as it demonstrates that a well-designed composite reinforcement system can outperform any single-carbide approach. I find the dilution control aspect of the PTA process to be the key differentiator compared to conventional hardfacing methods; without the ability to maintain low dilution, the carefully designed carbide composition would be compromised. For engineers selecting cladding solutions for wear-critical applications, this study provides a clear roadmap: identify the dominant wear mechanism, select appropriate carbide reinforcements, and employ a low-dilution deposition process to preserve the intended microstructure. The findings are directly applicable to components such as crusher liners, grinding mill liners, and mining equipment wear parts where severe abrasive conditions prevail.