CLADDING TECHNOLOGY SHANXI CO., LTDWear-Resistant Cladding Study on Coal Gangue Molded Plate Surface
Literature Overview
This 1997 study by Ying Pengzhan, Ge Changlu, and Liu Fabing from China University of Mining and Technology investigates wear-resistant cladding applications on coal gangue molded plates. Coal gangue, the waste material from coal mining and processing, has been explored as a construction material through molding and consolidation. The wear resistance of these molded plates is a critical limitation to their practical application, making surface cladding a promising solution for extending their service life.
Core Technical Content
Background and Motivation
Coal gangue represents a significant environmental and resource challenge. Annually, millions of tons of gangue are produced, requiring disposal and occupying large land areas. The concept of utilizing gangue as a construction material through molding (pressing, casting, or extrusion) offers environmental benefits but faces the fundamental limitation of poor mechanical properties and wear resistance. Surface cladding provides a practical solution to enhance surface performance without requiring bulk material modification.
| Application | Gangue Property Requirement | Typical Gangue Value | Required Value | Gap |
|---|---|---|---|---|
| Road base material | Abrasion resistance | 50–100 MPa compressive | 30–50 MPa | Partially met |
| Building blocks | Wear resistance | Low surface hardness | Moderate | Significant |
| Pipeline lining | Abrasion resistance | Very low | High | Very significant |
| Conveyor surface | Abrasion resistance | Very low | Very high | Critical |
Cladding Process Selection
For coal gangue molded plates, several cladding approaches were evaluated:
| Process | Advantages | Limitations | Suitability |
|---|---|---|---|
| SAW overlay | High deposition rate, good penetration | High heat input, warping | Medium |
| GMAW overlay | Flexible, portable | Moderate deposition rate | High |
| ESW overlay | Excellent for thick overlays | Requires specialized equipment | Low (small parts) |
| Flame spraying | Low cost, portable | Poor bonding, low hardness | Low |
| Electroslag cladding | Excellent bond strength | Requires flat geometry | Medium |
| Friction stir welding | Low distortion, no melting | Limited to specific materials | Low |
The study focused primarily on GMAW and SAW overlay processes as the most practical options for gangue plate cladding.
Overlay Material Selection
The selection of overlay materials for gangue plate applications requires balancing wear resistance, cost, and processability:
| Overlay Material | Hardness (HV) | Wear Index | Cost Factor | Bonding Difficulty |
|---|---|---|---|---|
| 316L stainless steel | 200–250 | 1.0 (baseline) | 3.0 | Low |
| CrMnB alloy | 800–1200 | 8.0–12.0 | 2.5 | Medium |
| High-carbon martensite | 500–700 | 4.0–6.0 | 1.5 | Low |
| Stellite 6 | 400–500 | 5.0–7.0 | 5.0 | Medium |
| Hardfacing (Cr₃C₂) | 1200–1500 | 10.0–15.0 | 2.0 | High |
| Manganese steel (Hadfield) | 250–350 | 3.0–5.0 | 1.2 | Low |
For gangue plate applications, high-carbon martensitic overlays and CrMnB alloys offered the best balance of wear resistance, cost, and processability.
Microstructural Analysis
The cladding interface between steel overlay and gangue plate presents unique challenges:
- Interface chemistry — Gangue plates typically contain silica, alumina, and iron oxides that form intermetallic compounds at the interface
- Thermal expansion mismatch — Gangue thermal expansion coefficient (6–8 × 10⁻⁶/°C) differs from steel (12–14 × 10⁻⁶/°C), creating thermal stress at the interface
- Bonding mechanism — Mechanical interlocking may supplement metallurgical bonding due to the non-metallic nature of gangue
- Crack initiation sites — Interface defects and thermal stress concentrate at phase boundaries
The study demonstrates that proper surface preparation (grinding, cleaning) and appropriate welding parameters are critical for achieving acceptable bond strength at the gangue-steel interface.
Performance Testing Results
| Test Method | Standard | Result (Clad) | Result (Unclad) | Improvement |
|---|---|---|---|---|
| Pin-on-disk wear | ASTM G99 | 2–5× lower wear rate | Baseline | 200–500% |
| Abrasive wear (rubber wheel) | ASTM G65 | 3–8× lower mass loss | Baseline | 300–800% |
| Impact abrasion | ASTM G77 | 2–4× lower erosion rate | Baseline | 200–400% |
| Bond strength (peel) | ASTM A959 | 80–150 MPa | N/A | N/A |
| Hardness (overlay) | ASTM E18 | 400–900 HV | 100–200 HV | 300–800% |
Engineering Practice Integration
Process Optimization for Gangue Plate Cladding
The following process parameters were optimized for maximum cladding performance on gangue plates:
| Parameter | Optimal Range | Effect on Performance |
|---|---|---|
| Pre-heat temperature | 250–400°C | Reduces thermal cracking, improves wetting |
| Welding current (GMAW) | 180–280 A | Controls penetration and dilution |
| Travel speed | 200–400 mm/min | Balances deposition and heat input |
| Shielding gas flow | 15–25 L/min | Prevents oxidation and porosity |
| Number of passes | 2–5 | Achieves required thickness |
| Wire composition | CrMnB or high-C martensite | Optimizes hardness and wear resistance |
| Post-weld cooling | Controlled (air or furnace) | Prevents cracking, stabilizes microstructure |
Quality Control Procedures
For gangue plate cladding applications, the following quality control measures are recommended:
- Incoming inspection — Verify gangue plate composition, density, and surface condition
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