Ni60-Cr3C2-WC/TiC Plasma Weld Overlay Wear Resistance Study and Application Technology
1. Definition and Fundamental Principles
Ni60-Cr3C2-WC/TiC plasma weld overlay is an advanced composite hardfacing technology that combines a nickel-based matrix alloy (Ni60, conforming to AWS A5.15 ENi-CI or ENi-CFe classifications) with dual-phase ceramic reinforcement particles—chromium carbide (Cr3C2) and tungsten carbide/titanium carbide (WC/TiC). This overlay is applied via plasma arc welding (PAW) or transfer-mode plasma arc welding (TPAW), where a high-temperature plasma jet (typically 10,000–30,000 K) melts the wire or powder feedstock and the base metal substrate simultaneously, creating a metallurgically bonded overlay layer with exceptional wear resistance properties.
The fundamental principle relies on the synergistic hardening mechanism of the composite system:
- Ni60 Matrix: Provides excellent corrosion resistance, thermal shock tolerance, and ductility as the binder phase. The high nickel content (≥56%) ensures solid solution strengthening and maintains a stable austenitic microstructure even under elevated temperatures.
- Cr3C2 Reinforcement: Acts as primary abrasion-resistant phases with hardness exceeding HV 1,800. Chromium carbides form a protective Cr2O3 oxide film during sliding wear, significantly reducing adhesive wear and oxidation wear rates.
- WC/TiC Reinforcement: Tungsten carbide (HV 2,200–2,500) provides extreme hardness for cutting and grinding wear resistance. Titanium carbide (HV 2,800–3,200) enhances thermal stability and prevents WC decomposition at high temperatures, forming a stable composite carbide network.
The plasma arc welding process ensures controlled heat input, minimal dilution of the base metal (typically 8–25%), and the ability to deposit uniform layers with controlled microstructure. The rapid solidification rates achievable in plasma welding (10^3–10^4 K/s) promote fine grain formation and uniform distribution of ceramic particles within the nickel matrix.
2. Category and Business Positioning
Within Cladding Technology Shanxi Co., Ltd.'s technical portfolio, the Ni60-Cr3C2-WC/TiC plasma weld overlay falls under the Weld Overlay (Hardfacing) Technology Route, specifically categorized as a composite-reinforced hardfacing process. This positions the company at the forefront of advanced surface engineering solutions for extreme wear environments.
The business positioning of this technology is threefold:
- High-Value Surface Engineering: Targeting industries where conventional hardfacing (e.g., Ni60 alone or Cr-based hardfacing) fails to meet extended service life requirements—mining, cement, power generation, and heavy manufacturing.
- Technical Differentiation: The dual-ceramic reinforcement (Cr3C2 + WC/TiC) represents a proprietary formulation that distinguishes the company's offerings from standard AWS/ENi-classified hardfacing consumables available in the market.
- Process Expertise Platform: Plasma arc welding overlay serves as a versatile platform technology that can be adapted to various substrate geometries, alloy systems, and production scales, supporting the company's broader qualification portfolio.
3. Technical Purpose and Value
3.1 Primary Technical Objectives
- Achieve overlay hardness of HV 900–1,200 (composite microstructure) with ceramic particle hardness exceeding HV 2,000
- Reduce abrasive wear rate by 60–80% compared to uncoated steel substrates
- Maintain overlay integrity under thermal cycling conditions (up to 600°C for Ni60 matrix, with ceramic phases stable to 800°C)
- Ensure metallurgical bonding strength exceeding 400 MPa at the overlay-substrate interface
- Achieve overlay thickness of 1–5 mm with controlled dilution and minimal residual stress
3.2 Economic and Operational Value
- Extended Component Life: 3–8× improvement in service life for high-wear components (crushers, chutes, hammers, mills), reducing unplanned downtime
- Reduced Maintenance Costs: Elimination of frequent replacement cycles translates to significant lifecycle cost savings
- On-Site and Shop Application Flexibility: Plasma arc welding can be performed in both manufacturing facilities and field conditions, accommodating large components that cannot be shipped
- Material Efficiency: Only the wear surface is upgraded, preserving the bulk structural integrity and reducing material consumption
4. Key Process and Implementation Points
4.1 Consumable Formulation Parameters
| Parameter | Ni60 Matrix | Cr3C2 Addition | WC/TiC Addition | Composite Target |
|---|---|---|---|---|
| Composition (Ni60 base) | Ni ≥56%, Cr 6–10%, Fe bal., C 2.0–3.0% | — | — | Per AWS A5.15 ENi-CI/ENi-CFe |
| Ceramic Content | — | 15–30 wt% Cr3C2 | 10–25 wt% WC/TiC | Total ceramics: 25–45 wt% |
| Ceramic Particle Size | — | 5–50 μm | 5–63 μm | Bimodal distribution for optimal packing |
| Form Factor | Wire or powder | Powder (pre-mixed or added to torch) | Powder (pre-mixed or added to torch) | Pre-blended composite powder preferred |
4.2 Plasma Arc Welding Process Parameters
| Process Variable | Typical Range | Critical Control Notes |
|---|---|---|
| Plasma Gas Flow Rate | 4–8 L/min (Ar or Ar+He) | Controls arc stability and shielding; too high causes turbulence and porosity |
| Shielding Gas Flow Rate | 12–20 L/min (Ar or Ar+2% H2) | Must fully envelop arc zone; H2 addition increases heat input and fluidity |
| Welding Current | 150–400 A (transfer mode) | Higher current increases dilution; optimize for 15–25% dilution target |
| Welding Speed | 200–600 mm/min | Controls heat input per unit length; higher speed reduces dilution but may cause incomplete fusion |
| Wire/Feed Speed | 300–800 mm/min | Must synchronize with welding speed for consistent layer thickness |
| Travel Angle | 75–90° (wire lead angle 10–20°) | Controls penetration profile and bead shape |
| Interpass Temperature | ≤250°C (strictly controlled) | Critical for preventing carbide coarsening and maintaining microstructure |
| Preheat Temperature | 100–200°C (for thick/low-conductivity substrates) | Reduces thermal shock and cracking risk on high-carbon or thick sections |
| Layer Thickness per Pass | 0.8–1.5 mm | Multi-pass build-up for total thickness of 2–5 mm |
4.3 Critical Implementation Steps
- Substrate Preparation: Machining the base metal to a smooth finish (Ra ≤ 12.5 μm), removal of contaminants (oil, rust, paint) via mechanical or chemical cleaning, and preheating as required.
- Transition Layer Application (if required): For dissimilar substrates (e.g., carbon steel to Ni60 overlay), a transition layer of 309L or Ni-based alloy may be deposited first to prevent cracking and ensure metallurgical compatibility per ASME Section IX requirements.
- Composite Overlay Deposition: Multi-pass application of the Ni60-Cr3C2-WC/TiC composite, maintaining interpass temperature control and consistent process parameters throughout.
- Post-Weld Heat Treatment (PWHT): Optional solution treatment at 900–1050°C followed by controlled cooling to optimize microstructure and relieve residual stresses, particularly for thick overlay builds.
- Machining and Finishing: Post-overlay machining to achieve dimensional tolerances (typically ±0.1–0.3 mm) and surface finish requirements (Ra 1.6–6.3 μm for sliding applications).
5. Applicable Standards and Acceptance Criteria
5.1 Governing Standards
| Standard | Scope of Application |
|---|---|
| AWS A5.15 | Specification for Nickel and Nickel Alloy Welding Electrodes and Rods (Ni60 classification) |
| ASTM A388 | Standard Specification for Steel Plate, Clad for Pressure Vessels (when overlay applied to pressure vessel components) |
| ASME Section IX, Part Q | Qualification of Welding Procedure Specifications for Overlay Welding |
| NB/T 47014 | Procedure Qualification Test for Welding of Pressure Vessel (Chinese standard for WPS qualification) |
| GB/T 12469 | Welding Consumables—Specification for Nickel and Nickel Alloy Welding Rods |
| GB/T 11345 | Non-Destructive Testing of Welds—Ultrasonic Testing Method |
| ISO 9093-1 | Non-Destructive Testing of Welds—Ultrasonic Testing—Procedure Recommendations, Part 1 |
| NACE MR0175/ISO 15156 | Materials for Use in H2S-Containing Environments in Oil and Gas Production (when applicable) |
| ASTM G99 | Standard Test Methods for Laboratory Abrasion Testing (dry sand/rubber wheel wear testing) |
| ASTM G85 | Standard Test Method for Pin-on-Disk Wear Testing of Hardened Steels |
5.2 Acceptance Criteria
- Visual Inspection (VT): No visible cracks, excessive spatter, undercut, or incomplete fusion at the overlay-substrate interface. Bead profile within specified dimensions per WPS.
- Ultrasonic Testing (UT): Per GB/T 11345 or ISO 9093-1, no indications of delamination, lack of fusion, or cracks exceeding acceptance thresholds (typically no level II indications).
- Hardness Testing: HV 900–1,200 for the composite overlay (measured per ASTM E92 or GB/T 1838.1); individual ceramic particles ≥HV 1,800.
- Dilution Control: Maximum 25% base metal dilution into the first overlay layer; subsequent layers ≤15%.
- Microstructural Examination: Uniform distribution of Cr3C2 and WC/TiC particles; no excessive carbide network at grain boundaries; absence of brittle phases (e.g., sigma phase).
- Wear Testing: Abrasive wear rate ≤0.5 mg/N·m (ASTM G99 dry sand/rubber wheel) for qualification purposes.
6. Common Risks and Controls
6.1 Process Risks
| Risk | Cause | Control Measure |
|---|---|---|
| Overlay cracking (hot/cold) | High dilution, excessive interpass temperature, low-ductility ceramic-rich zones | Control dilution ≤25%; maintain interpass ≤250°C; consider transition layer; optimize Ni60 matrix composition for ductility |
| Porosity | Inadequate shielding, excessive travel speed, contaminated consumables | Ensure gas flow rates per WPS; use dry, properly stored consumables; maintain stable arc conditions |
| Uneven ceramic distribution | Segregation during melting, poor powder blending, high current causing particle dissolution | Pre-blend consumables with controlled particle size distribution; optimize current density; consider powder feeding vs. wire feeding |
| Excessive dilution | High current, low travel speed, deep penetration settings | Reduce current; increase travel speed; use back-of-bead technique; apply transition layer |
| Ceramic dissolution/decay | Excessive heat input, prolonged exposure at high temperature | Minimize heat input per pass; control interpass temperature; use multiple thin passes rather than single thick deposit |
| Residual stress-induced spalling | Mismatch in thermal expansion coefficients, high heat input | Post-weld stress relief (600–700°C for 1–2 hours); controlled cooling; multi-pass with alternating directions |
6.2 Quality Assurance Controls
- Implement a documented WPS (Welding Procedure Specification) qualified per ASME Section IX Part Q or NB/T 47014
- Qualify WPQ (Welder Performance Qualification) for plasma arc welding with composite consumables
- Maintain traceability of consumable lots with mill certificates and composition analysis
- Conduct in-process hardness spot checks every 500 mm of overlay to detect parameter drift
- Perform 100% UT inspection on critical applications; 10% sampling for standard applications
7. Application Scenarios Across Company Technology Routes
7.1 TIG/MIG Weld Overlay Route (Primary Application)
The Ni60-Cr3C2-WC/TiC plasma weld overlay is the flagship application within the TIG/MIG weld overlay technology route. Specific application scenarios include:
- Mining Equipment: Hardfacing of jaw crusher plates, cone crusher mantles, shovel teeth, and conveyor rollers subjected to abrasive rock and ore. The composite overlay extends service life from 3–6 months to 18–36 months in abrasive mineral processing applications.
- Cement Industry: Overlay of mill liners, feed chutes, rotary kiln wear plates, and fan blades in high-abrasion, moderate-temperature environments. The Ni60 matrix provides thermal stability while ceramic particles resist abrasive cement slurry.
- Power Generation: Hardfacing of boiler tubes, coal mill rollers, and fly ash handling components. The Ni60 base provides corrosion resistance in flue gas environments while ceramics resist fly ash abrasion.
- Heavy Manufacturing: Surface protection of extrusion dies, forging dies, and stamping tools where moderate impact loading combined with abrasive wear is present.
7.2 Hydraulic Explosive Bonding Route
While the Ni60-Cr3C2-WC/TiC overlay is primarily a weld overlay technology, the wear resistance research findings directly inform and complement the hydraulic explosive bonding route:
- Surface Preparation for Bonding: The wear resistance data obtained from the plasma overlay study provides critical input for selecting appropriate surface preparation and conditioning treatments on clad plates fabricated by hydraulic explosive bonding. Understanding the tribological behavior of Ni60-based materials ensures that explosively bonded Ni60/steel clad plates are properly finished and deployed in service.
- Post-Bonding Surface Enhancement: In hybrid fabrication approaches, hydraulic explosive bonding creates the base clad plate (e.g., Ni60/Carbon Steel), and subsequent plasma arc weld overlay with the composite Ni60-Cr3C2-WC/TiC formulation provides additional surface hardening on high-wear zones of the bonded assembly. This creates a multi-layer composite structure combining the ductility of explosive bonding with the extreme hardness of the composite overlay.
- Material Compatibility Data: The metallurgical studies conducted during the plasma overlay research—particularly regarding dilution behavior, interfacial microstructure, and bonding strength—provide transferable knowledge for optimizing hydraulic explosive bonding parameters where Ni60-based cladding materials are used.
7.3 Explosion Welding Route
The research findings from the Ni60-Cr3C2-WC/TiC plasma overlay study contribute to the explosion welding route in the following ways:
- Clad Plate Surface Conditioning: Explosion-welded Ni60 clad plates (e.g., Ni60/16Mn or Ni60/304SS) can be further enhanced with the composite plasma overlay on critical wear surfaces, creating a graded hardness profile from the explosion-welded base to the ultra-hard composite surface.
- Performance Benchmarking: Wear testing data from the plasma overlay provides comparative benchmarks for evaluating the inherent wear resistance of explosion-welded Ni60 cladding, guiding customers on when to select explosion welding alone versus explosion welding plus surface hardfacing.
- Repair and Maintenance: Field-damaged explosion-welded clad components can be repaired using the plasma overlay technology, restoring wear resistance to original specifications without requiring full component replacement.
8. Contribution to Qualification Building, Product Delivery, and Customer Value
8.1 Qualification Building
- WPS Qualification Expansion: The research establishes the technical basis for qualifying new Welding Procedure Specifications covering composite hardfacing applications, expanding the company's certified WPS library and enabling acceptance of more complex customer requirements.
- NDT Method Validation: Development of inspection protocols specifically for composite hardfacing layers (where ceramic inclusions may produce UT signal artifacts) strengthens the company's NDT capabilities and accreditation scope.
- Third-Party Certification: Research documentation supports applications for certifications from bodies such as ASME, CNAS (China National Accreditation Service), and industry-specific bodies (e.g., API for oil and gas applications).
8.2 Product Delivery Enhancement
- Process Standardization: The research translates into documented process cards, operator training materials, and quality control checklists that ensure consistent product quality across multiple production shifts and facilities.
- Consumable Development: Findings on optimal ceramic content, particle size, and distribution guide the development of proprietary composite welding consumables that are optimized for the company's specific plasma welding equipment and process parameters.
- Accelerated Testing Protocols: Established wear testing methodologies enable rapid qualification of new overlay formulations for specific customer applications, reducing time-to-market for customized solutions.
8.3 Customer Value Delivery
- Technical Consultation Capability: Detailed wear resistance data enables the company to provide evidence-based recommendations to customers regarding overlay selection, thickness, and process parameters for their specific service conditions.
- Performance Guarantee: Quantified wear rate data (mg/N·m, mm³/N·m) provides the technical foundation for offering performance guarantees and warranty extensions on overlay services.
- Total Cost of Ownership Reduction: The demonstrated 60–80% improvement in wear resistance translates directly into reduced component replacement frequency, lower maintenance labor, and minimized production downtime for customers—delivering compelling ROI that differentiates the company in competitive bids.
- Intellectual Property: Proprietary formulations and process parameters developed through this research can be protected through patents, creating long-term competitive advantages and revenue streams from technology licensing.
9. Conclusion and Future Development Directions
The Ni60-Cr3C2-WC/TiC plasma weld overlay research represents a critical capability node within Cladding Technology Shanxi Co., Ltd.'s technical ecosystem. By bridging fundamental materials science with practical manufacturing implementation, this research enables the company to deliver next-generation surface engineering solutions that address the most demanding wear environments encountered in heavy industry.
Future development directions include:
- Development of gradient composite overlays with controlled ceramic content variation through the overlay thickness
- Integration with robotic plasma welding systems for automated, repeatable production-scale overlay application
- Extension of the composite formulation to include additional reinforcing phases (e.g., SiC, B4C) for ultra-high temperature and chemical resistance applications
- Digital twin modeling of overlay deposition to predict microstructure and wear performance based on process parameter inputs