CLADDING TECHNOLOGY SHANXI CO., LTDManufacturing Wear-Resistant Composite Steel Plates Using Powder-Filler Overlay Method
Literature Overview
This 2001 study published in Engineering and Materials by researchers from Beijing University of Technology, the Chinese Academy of Agricultural Mechanization Sciences, and Tangshan Cement Machinery Factory presents a practical approach to manufacturing wear-resistant composite steel plates using a powder-filler overlay welding technique. The research addresses the need for cost-effective, scalable production of bimetallic composite plates for agricultural machinery and industrial applications.
The powder-filler overlay method combines conventional arc welding with in-situ powder addition to the weld pool, enabling the creation of hardfacing layers with tailored compositions and microstructures without requiring specialized equipment. This approach offers significant economic advantages over cladding plate rolling or explosion welding for smaller production volumes and custom applications.
Core Technical Content
Process Description
The powder-filler overlay method involves the following key steps:
- Powder preparation: A hardfacing powder blend is prepared with controlled composition, particle size distribution (typically 40–150 μm), and spherical morphology.
- Substrate preparation: The carbon steel base plate is surface prepared by grinding or shot blasting to remove scale and contaminants.
- Overlay application: Powder is fed into the arc zone during GMAW or FCAW welding, where it melts and alloys with the base metal to form the composite layer.
- Multi-pass welding: Multiple passes are applied to achieve the required overlay thickness (typically 5–15 mm).
Powder Composition and Microstructure
| Powder Component | Content (wt%) | Function |
|---|---|---|
| Cr | 18–25 | Carbide former, solid solution strengthening |
| C | 2.5–4.0 | Primary carbide former |
| Mo | 2–4 | Secondary hardening, carbide stabilization |
| Ni | 3–6 | Austenite stabilizer, toughness improvement |
| Mn | 2–4 | Deoxidizer, grain refiner |
| Fe | Balance | Matrix material |
The resulting overlay microstructure consists of:
- Primary carbides: M7C3 type, 20–50 μm in size, distributed throughout the overlay
- Secondary carbides: M23C6 and M6C, 2–10 μm, formed during solidification and cooling
- Matrix: Mixture of martensite (50–70%) and retained austenite (15–30%)
- Carbide volume fraction: 35–50%
Mechanical Properties
| Property | Base Plate (Q235) | Overlay Layer | Bond Zone |
|---|---|---|---|
| Hardness (HV30) | 130–160 | 650–750 | 280–350 |
| Tensile strength (MPa) | 370–500 | N/A (too hard) | 550–650 |
| Impact energy (J) | 47–80 | 8–15 | 35–55 |
| Elongation (%) | 25–32 | 2–5 | 12–18 |
The overlay layer achieves 4–5 times the hardness of the base material while maintaining acceptable impact energy for most wear applications.
Production Parameters
| Parameter | Value | Notes |
|---|---|---|
| Welding method | GMAW (short arc) | Flux-cored wire available |
| Wire diameter | 1.2–1.6 mm | Match to powder feed system |
| Current | 180–250 A | DCEN polarity |
| Voltage | 22–28 V | Stable arc required |
| Travel speed | 200–400 mm/min | Depends on desired penetration |
| Powder feed rate | 150–300 g/min | Adjusted for desired dilution |
| Shielding gas | Ar + 2% CO2 | Reduces oxidation, improves wetting |
| Preheat | 100–150°C | Reduces cracking risk |
| Interpass temp | < 200°C | Control cooling rate |
Bond Strength and Quality
| Test Method | Standard | Acceptance Criteria | Typical Result |
|---|---|---|---|
| Bend test | GB/T 2651 | No cracking at 180° bend | Pass |
| Peel test | ASTM A264 | ≥ 90% of base tensile strength | 92–98% |
| Shear test | ASTM A264 | ≥ 0.8 × base shear strength | 0.85–0.95× |
| Hardness profile | Per specification | Gradual transition, no soft zone | Acceptable |
Engineering Practice Implications
Cost-Benefit Analysis
| Method | Cost Index (relative) | Production Rate | Flexibility | Quality Consistency |
|---|---|---|---|---|
| Roll-bonded cladding | 100 | High (continuous) | Low (standard sizes) | Excellent |
| Explosion welding | 80 | Medium | Medium | Good |
| Powder-filler overlay | 45 | Medium | High (custom shapes) | Good (with QC) |
| Strip cladding | 70 | High | Low | Excellent |
The powder-filler overlay method offers the best cost-performance ratio for custom shapes, small batch production, and repair applications where standard cladding plate dimensions are not available.
Quality Control Plan
- Incoming inspection: Verify powder composition by chemical analysis (ICP-OES), particle size distribution (laser diffraction), and moisture content (< 0.1%).
- Process monitoring: Record welding parameters for each pass, monitor arc stability, and check powder feed consistency.
- In-process inspection: Visual examination of each pass for porosity, undercut, or incomplete fusion.
- Final inspection: Hardness testing (3 points per 300 mm), metallographic examination of cross-section, bond strength testing per specification.
- Traceability: Maintain welder qualification records, powder lot traceability, and test reports for each production batch.
Common Defects and Solutions
| Defect | Cause | Solution |
|---|---|---|
| Surface porosity | Gas entrapment, powder moisture | Dry powder, improve shielding, preheat |
| Cracking | High carbon, rapid cooling | Preheat, control interpass temperature |
| Poor fusion | Low current, high travel speed | Increase current, reduce travel speed |
| Uneven hardness | Inconsistent powder feed | Calibrate feeder, monitor feed rate |
| Base metal burn-through | Excessive penetration | Reduce current, increase travel speed |
Study Insights and Reflections
The powder-filler overlay method represents a pragmatic approach to composite plate manufacturing that bridges the gap between expensive specialized cladding processes and basic welding operations. Its flexibility in accommodating custom geometries and varying overlay compositions makes it particularly suitable for agricultural machinery, mining equipment, and industrial wear parts.
A key insight from this research is the importance of powder quality control. Unlike conventional welding consumables, hardfacing powders must maintain consistent composition, particle size, and morphology to ensure repeatable overlay properties. Powder suppliers should provide certificates of analysis with each lot, and incoming inspection should verify critical parameters.
For pressure vessel applications, the powder-filler overlay method can be used for localized repair and reinforcement of worn areas. However, full overlay of pressure vessel components requires careful consideration of code requirements (NB/T 47002, ASME VIII Div.1) regarding weld procedure qualification, material specifications, and inspection requirements. The method is more commonly applied to non-pressure-bearing wear components such as manway covers, support structures, and external attachments.
The study also demonstrates that overlay thickness has a significant effect on service life but with diminishing returns beyond a certain point. For most applications, 8–12 mm provides adequate wear life while minimizing material cost and residual stress concerns.