Microstructure and Properties of TiC-VC Enhanced Wear-resistant Cladding with Novel Dual Deposition Electrodes

Literature Overview

The present study examines a novel dual deposition electrode technique for producing TiC-VC enhanced wear-resistant cladding layers. Dual deposition electrodes represent an advanced welding consumable technology that combines two distinct electrode materials within a single electrode body, enabling the simultaneous deposition of two different alloy compositions in a single welding pass. This approach offers significant advantages in terms of process efficiency, dilution control, and microstructural engineering. The study focuses on the microstructural evolution, hardness distribution, and wear resistance of the resulting cladding layer, providing insights into the design and application of dual electrode systems for tribological applications.

Core Technical Points

Dual Deposition Electrode Design

The dual deposition electrode under investigation consists of an outer sheath of TiC-reinforced alloy and an inner core of VC-reinforced alloy, both embedded within a flux-cored welding wire configuration. The outer sheath material provides the primary wear-resistant phase (TiC) with high hardness and chemical stability, while the inner core material (VC) contributes additional carbide reinforcement and modifies the matrix composition. The electrode geometry is designed such that the outer sheath melts first during the welding arc, forming the initial deposited layer, while the inner core melts subsequently, creating a layered or intermixed microstructure.

The dual electrode system eliminates the need for separate consumable materials and multiple welding passes, significantly reducing production costs and improving process repeatability. The electrode diameter was 1.6 mm with a total length of 300 mm, and the flux cored wire configuration provided stable arc characteristics and consistent deposition rates.

Microstructural Characteristics

The microstructure of the dual deposition cladding layer exhibits a distinctive layered morphology that reflects the sequential melting and solidification of the two electrode materials. The outer region, derived primarily from the TiC-reinforced sheath, contains coarse TiC particles (20–80 μm) embedded in a martensitic matrix. The inner region, derived from the VC-reinforced core, features finer VC particles (5–30 μm) distributed within a finer-grained martensitic structure. At the interface between the two regions, a transition zone with mixed TiC-VC particles is observed, indicating partial intermixing during solidification.

The matrix microstructure consists predominantly of tempered martensite with retained austenite in the range of 5–12%, depending on the local composition. The retained austenite content is particularly significant at the interface region, where the combined carbon and alloying element content from both electrode materials stabilizes the austenite phase. This retained austenite contributes to the overall toughness of the cladding layer by providing a transformation-induced plasticity mechanism during wear.

Wear Resistance Performance

The wear resistance was evaluated using a pin-on-disk tribometer under both dry sliding and abrasive conditions. The TiC-VC enhanced cladding layer demonstrated a wear rate of 0.8 × 10⁻⁶ mm³/N·m under dry sliding conditions, which is approximately 60% lower than that of a conventional single-electrode TiC cladding layer (2.0 × 10⁻⁶ mm³/N·m). Under abrasive wear conditions (SiC abrasive paper, 2000 grit), the dual electrode cladding exhibited a wear rate of 1.5 × 10⁻⁶ mm³/N·m, compared to 3.2 × 10⁻⁶ mm³/N·m for the conventional cladding.

The improved wear resistance is attributed to the synergistic effect of two distinct carbide phases. TiC particles, with their high hardness (2800 HV) and excellent thermal stability, provide primary wear resistance against abrasive contacts. VC particles, with their high hardness (2850 HV) and finer size distribution, contribute to a more uniform load distribution and reduced matrix softening. The combination results in a composite-like wear mechanism where the hard carbide phases bear the majority of the applied load, while the ductile martensitic matrix absorbs energy and prevents carbide fracture.

Hardness Distribution

The hardness profile across the cladding layer shows a gradient from the surface to the substrate. The outer TiC-rich region exhibits a hardness of 750–820 HV, while the inner VC-rich region reaches 780–850 HV. The transition zone displays a hardness of 720–780 HV. The substrate hardness (low-carbon steel) is approximately 180–220 HV. The hardness gradient provides a smooth transition in mechanical properties, reducing the risk of stress concentration at the cladding-substrate interface.

The hardness values are significantly higher than those of conventional single-carbide cladding layers (typically 600–700 HV), confirming the effectiveness of the dual carbide reinforcement strategy. The hardness improvement is primarily due to the higher volume fraction of carbide particles (approximately 35–40%) achieved through the dual electrode approach, compared to 20–25% in conventional single-carbide systems.

Engineering Practice and Process Considerations

The dual deposition electrode technique offers several practical advantages for industrial applications. The single-pass deposition capability reduces the number of welding passes required, thereby minimizing the thermal cycles imposed on the substrate and reducing the risk of hydrogen-induced cracking and distortion. The consistent microstructure achieved with a single electrode type simplifies quality control and reduces the variability associated with multi-pass welding operations.

However, several process challenges must be addressed in engineering practice. The dual electrode requires precise control of welding parameters to ensure uniform melting of both the outer sheath and inner core materials. Insufficient current or excessive travel speed can result in incomplete melting of the inner core, leading to a non-uniform microstructure with segregated regions of TiC and VC. Conversely, excessive current can cause overheating and carbide dissolution, reducing the volume fraction of the wear-resistant phases.

The recommended welding parameters (220–280 A, 22–28 V, 150–250 mm/min) represent a narrow process window that requires careful calibration for each specific application. Preheating the substrate to 150–200°C is recommended to minimize the risk of cracking in the heat-affected zone, particularly when welding on low-alloy steel substrates with carbon equivalents exceeding 0.4%. Post-weld heat treatment (tempering at 500–550°C for 1–2 hours) is advisable to relieve residual stresses and stabilize the martensitic microstructure, although this may slightly reduce the peak hardness by 50–80 HV.

Key Questions and Reflections

The study raises important considerations regarding the scalability and consistency of the dual deposition electrode technique. The electrode manufacturing process itself requires precise control of the sheath-to-core ratio and the homogeneity of carbide distribution within each electrode segment. Variations in electrode manufacturing quality can lead to significant differences in cladding performance, which is a concern for high-volume production applications.

Another critical question concerns the long-term stability of the carbide phases under elevated temperature service conditions. TiC is known to be thermally stable up to approximately 1000°C, while VC begins to decompose above 800°C. For applications involving sustained temperatures above 800°C, the VC component may undergo phase transformation, leading to a gradual loss of wear resistance. The study does not extensively address this thermal stability issue, which warrants further investigation for high-temperature applications.

The dilution behavior of the dual electrode system also merits attention. The dual electrode technique inherently reduces dilution compared to conventional solid electrode welding, but the dilution level still depends on the welding parameters and substrate thermal properties. For thick substrate sections, the dilution can reach 15–20%, which may dilute the carbide content and reduce the effective hardness of the cladding layer. Engineers should account for this by adjusting the welding parameters or by applying multiple passes to maintain the desired carbide volume fraction.

Study Insights and Implications

This literature demonstrates that the dual deposition electrode technique is a promising approach for producing high-performance wear-resistant cladding layers with enhanced microstructural complexity and improved tribological properties. The synergistic effect of TiC and VC carbide phases, combined with the efficient single-pass deposition capability, makes this technology particularly attractive for applications requiring high wear resistance in a cost-effective manner. Engineers should consider the dual electrode approach as a viable alternative to conventional multi-pass cladding operations, particularly for repair and refurbishment work where process efficiency and consistent quality are paramount. However, careful attention must be paid to electrode quality control, welding parameter optimization, and post-weld heat treatment to ensure reliable performance in service. The technology holds significant potential for extending the service life of components in mining, construction, and power generation industries, where abrasive and adhesive wear are the primary failure modes.