High Wear-Resistant Cladding Technology: Composite Material Plasma Arc Cladding and Current Status

Literature Overview

The study by Zhao Kun and Cheng Zhiguo from the Harbin Welding Institute, published in Welding (1999), provides a comprehensive review of composite material plasma arc cladding technology for high wear-resistant applications. This work represents an important milestone in the development of plasma transferred arc (PTA) powder cladding technology in China, documenting the state of the art at the time and outlining future development directions.

Process Fundamentals

Plasma arc cladding uses a high-velocity plasma jet to melt powder feedstock and the substrate surface, creating a dilution-controlled cladding layer. The plasma arc operates at temperatures of 10,000-30,000 K, providing intense but focused heat input that minimizes thermal distortion of the base component.

Composite Material Systems for Wear-Resistant Cladding

The review covers several composite material systems that have been developed for specific wear applications:

1. Cementite-reinforced austenite composites

• Matrix: High manganese austenite (11-14% Mn, 1.0-1.5% C)
• Reinforcement: M₇C₃, M₃C carbides formed in situ
• Application: Mining equipment, crusher components
• Hardness: 400-600 HV
• Advantage: Excellent impact-abrasion resistance through work hardening

2. WC-cobalt composites

• Matrix: Cobalt or cobalt-chromium alloy
• Reinforcement: WC particles (5-50 μm)
• Application: Cutting tools, die surfaces, valve seats
• Hardness: 800-1200 HV
• Advantage: Superior dry sliding wear resistance

3. Carbide-ceramic composites

• Matrix: Iron-based or nickel-based alloy
• Reinforcement: TiC, TiN, Al₂O₃, SiC particles
• Application: High-temperature wear applications
• Hardness: 600-1000 HV
• Advantage: Good high-temperature stability

4. Bimetallic composites

• Matrix: Low-carbon steel or nickel alloy
• Reinforcement: Hard phase particles or fibers
• Application: General wear protection
• Hardness: 400-800 HV
• Advantage: Good balance of toughness and hardness

Process Optimization for Composite Cladding

The key to successful composite material plasma arc cladding is the control of dilution and the preservation of the composite structure during the welding process.

Dilution control strategies:

• Lower arc current (100-200 A) reduces substrate melting
• Higher travel speed reduces heat input per unit length
• Powder preheating improves powder melting efficiency and reduces substrate interaction
• Back-plate cooling reduces heat conduction into the substrate
• Layer-by-layer deposition with controlled interpass cooling

Microstructure control:

• Rapid solidification from PTA produces fine-grained microstructures
• The dilution level directly affects the hardness and wear resistance of the composite
• Particle size and distribution in the powder blend influence the final microstructure
• Cooling rate affects the morphology of the reinforcing phase

Quality Assurance Considerations

For wear-resistant cladding applications, the following quality assurance measures are critical:

1. Hardness mapping: Cross-sectional hardness profiles from the substrate surface to the cladding surface must be measured at multiple locations to verify uniformity. The hardness transition zone from base metal to cladding should be gradual to avoid stress concentration.
2. Bond strength testing: Shear or tensile bond strength tests verify the metallurgical bond between the cladding and substrate. Minimum bond strength requirements vary by application but are typically 150-250 MPa for wear-resistant applications.
3. Porosity and defect evaluation: PTA cladding can produce porosity due to gas entrapment in the powder feed. Porosity reduces effective load-bearing area and can initiate fatigue cracks. Back-face porosity (between cladding layers) is particularly detrimental.
4. Microstructural examination: Metallographic analysis of the cladding cross-section verifies the microstructure, particle distribution, and absence of cracks or unmelted particles.
5. Wear testing: Pin-on-disk, sand rub, or abrasion wheel testing quantifies the wear resistance of the cladding surface. Results should be compared with the base material to establish the wear life improvement factor.

Industry Application Status

By the time of publication (1999), PTA composite cladding had found application in:

• Mining industry: Crusher hammers, jaw plates, conveyor rollers
• Cement industry: Mill liners, grinding elements, kiln wear parts
• Steel industry: Rolling mill rolls, guide plates, shear blades
• Energy industry: Boiler tubes, heat exchanger tubes, turbine components
• Aerospace: Engine components, landing gear surfaces

The technology offered distinct advantages over traditional arc welding cladding:

• Lower dilution (5-15% vs. 20-40% for SAW)
• Better microstructural control
• Lower heat input and reduced distortion
• Ability to apply thin, high-quality layers
• Suitable for complex geometries

Study Insights and Forward Looking Perspective

The 1999 review by Zhao and Cheng captures a transitional period in cladding technology. At that time, PTA was beginning to displace conventional arc welding processes for high-quality cladding applications, but it had not yet achieved the productivity levels of ESW or multi-wire SAW for thick deposits.

The fundamental insight from this work is that the selection of cladding process must be driven by the application requirements rather than process availability. For thin, high-quality cladding layers on complex geometries, PTA is the preferred process. For thick deposits on large flat surfaces, ESW or multi-wire SAW offers better productivity. The optimal solution often involves a hybrid approach combining different processes for different cladding thickness requirements.

From a modern perspective, several developments have occurred since 1999 that enhance the capabilities described in this review:

1. Multi-powder feed systems: Modern PTA systems can simultaneously feed multiple powder compositions, enabling graded or functionally graded cladding layers.
2. Hot-wire PTA: The addition of a hot-wire electrode to the PTA process increases deposition rate by 50-100% while maintaining low dilution.
3. Laser cladding: Laser cladding has emerged as a complementary technology offering even lower dilution (2-5%) and finer microstructures, though at lower deposition rates.
4. Advanced powder metallurgy: Improved powder production techniques (water atomization, gas atomization, plasma atomization) have expanded the range of available composite powder compositions.

The enduring value of this 1999 review lies in its systematic categorization of composite material systems and their wear mechanisms. The fundamental principles of composite cladding design—balancing matrix toughness with reinforcement hardness, controlling dilution to preserve composite structure, and matching material system to wear regime—remain valid and are now supported by more sophisticated characterization and simulation tools.

This work serves as a valuable historical reference and technical foundation for engineers evaluating plasma arc cladding technology for wear-resistant applications. The composite material systems described continue to be actively used in industry, and the process optimization principles outlined remain relevant to modern PTA practice.