Plasma Surfacing Repair Method for Conveyor Scraper Components

Literature Overview

This 2020 paper by Fang Min, Yang Hongfei, Ju Chen, and Yuan Changsuo, published in Coal Mine Machinery (煤矿机械), presents a comprehensive approach to repairing worn conveyor scrapers using plasma surfacing technology. The research combines three-dimensional surface reconstruction with plasma surfacing process planning, addressing the practical challenge of restoring irregularly worn scraper surfaces to functional condition. The work was conducted by Shendong Coal Group and Xi'an Fluente Heat Treatment Company.

Problem Statement and Engineering Challenge

Mining conveyor scrapers operate under severe wear conditions due to continuous friction with hard rock and mineral materials. The resulting wear surface presents unique challenges for repair:

The irregularity of the wear surface is the primary challenge, as conventional repair methods (grinding, machining) cannot efficiently restore the original geometry.

Three-Dimensional Surface Reconstruction Methodology

The research introduces a systematic approach to characterizing the worn surface:

Data Acquisition Process

1. Line laser scanning: High-resolution 3D scanning of the worn surface using a line laser scanner
2. Point cloud generation: Conversion of scan data into a three-dimensional point cloud representation
3. Data preprocessing: Removal of noise, outlier filtering, and coordinate system alignment
4. Surface reconstruction: Mathematical modeling of the worn surface geometry

Data Preprocessing Steps

The following preprocessing steps are applied to the raw scan data:

Three-Dimensional Reconstruction Output

The reconstructed surface model provides:

• Complete geometric representation of the worn surface
• Quantitative wear depth distribution map
• Identification of critical wear zones requiring maximum repair
• Input data for surfacing path planning

Plasma Surfacing Process Planning

Surfacing Path Planning Strategy

Based on the three-dimensional reconstruction data, the surfacing path is planned using the following approach:

1. Zonal classification: Division of the repair area into zones based on wear depth
2. Pass sequencing: Determination of optimal pass order for each zone
3. Overlap optimization: Setting appropriate bead overlap to ensure complete coverage
4. Heat input management: Balancing deposition rate with thermal control

Plasma Surfacing Parameters

Multi-Pass Surfacing Strategy

For areas with significant wear depth, a multi-pass strategy is employed:

Quality Assessment and Results

Bonding Interface Evaluation

The research reports strong bonding between the base metal and surfacing layer:

• Metallurgical bonding: Confirmed through metallographic examination
• Bond strength: Exceeds the tensile strength of the base material
• Interface quality: No porosity, lack of fusion, or cracking observed
• Transition zone: Gradual composition change indicating good metallurgical compatibility

Surfacing Layer Quality

Wear Performance Verification

The repaired scrapers demonstrate:

• Surface hardness exceeding the base material by 50% or more
• Wear resistance sufficient for return to service
• Surface finish compatible with conveyor operation
• No premature failure during service testing

Engineering Implementation Considerations

Equipment Requirements

Implementation Workflow

The complete repair process follows this workflow:

1. Disassembly and cleaning: Remove scraper from conveyor and clean surface
2. Baseline inspection: Document current condition and measure wear depth
3. 3D scanning: Acquire surface geometry data
4. Data processing: Reconstruct surface and plan repair path
5. Base preparation: Grind surface to remove loose material and contamination
6. Preheating: Apply controlled preheat to reduce cracking risk
7. Surfacing deposition: Execute planned surfacing passes
8. Post-heating: Controlled cooling to minimize residual stress
9. Finishing: Machine or grind surface to required geometry
10. Quality verification: Inspect and test repaired surface
11. Reinstallation: Return scraper to conveyor service

Cost-Benefit Analysis

The economic justification for plasma surfacing repair versus replacement includes:

Study Insights and Practical Implications

This research demonstrates the successful integration of advanced measurement technology with conventional surfacing processes to solve a practical industrial problem. The three-dimensional reconstruction approach provides a systematic method for handling irregular wear surfaces that cannot be addressed by conventional repair methods.

The combination of line laser scanning with plasma surfacing represents a paradigm shift in component repair philosophy, moving from simple material replacement to precision geometry restoration. This approach is particularly valuable for:

• Mining equipment with irregular wear patterns
• Large components where replacement is impractical
• Custom or obsolete components unavailable from manufacturers
• High-value components where repair is economically justified

The research also highlights the importance of systematic process planning in surfacing applications. The integration of measurement data with process parameters ensures that the repair is optimized for the specific wear condition encountered.

Summary

This study presents a comprehensive methodology for repairing worn conveyor scrapers using plasma surfacing technology guided by three-dimensional surface reconstruction. The successful combination of advanced measurement technology with plasma surfacing provides a practical solution for restoring irregularly worn components to functional condition. The demonstrated bonding quality, surface finish, and wear performance confirm the viability of this approach for industrial application. For mining operations and other industries facing component wear challenges, this methodology offers a cost-effective and environmentally responsible alternative to component replacement.