Weld Overlay Plate

Weld Overlay Plate is a composite wear-resistant steel product manufactured by depositing a high-hardness alloy layer onto a carbon steel or low-alloy steel base plate using advanced welding overlay techniques. It is widely used in mining, cement, power generation, steel plants, and bulk material handling industries where severe abrasion and impact conditions are present.

The performance of weld overlay plate depends heavily on the quality of the welding process, which determines the hardness, bonding strength, and wear resistance of the surface layer.

Overview of Weld Overlay Process

The weld overlay process is a surface engineering method that applies a wear-resistant alloy layer onto a steel substrate through controlled welding techniques. The process creates a strong metallurgical bond between the base metal and the overlay layer.

Main Welding Overlay Methods

1. Open Arc Welding (SAW / FCAW Overlay)

This is the most commonly used industrial method for producing weld overlay plates.

• Uses flux-cored wire or submerged arc welding
• High deposition rate
• Suitable for large-area production
• Produces uniform chromium carbide layers

Advantages:

• High efficiency
• Stable welding quality
• Cost-effective for mass production

2. Shielded Metal Arc Overlay (SMAW)

A manual welding method used for smaller components or repair work.

• Uses coated electrodes
• Flexible operation
• Suitable for complex shapes

Advantages:

• Low equipment requirement
• Good for repair and maintenance

Limitations:

• Lower efficiency compared to automated processes

3. Gas Metal Arc Welding (GMAW / MIG Overlay)

A semi-automatic or automatic process.

• Uses continuous wire feeding
• Controlled shielding gas environment
• Good surface quality

Advantages:

• Stable arc
• Good control of dilution
• Suitable for medium-scale production

4. Plasma Transferred Arc (PTA) Welding

A high-precision overlay method.

• Concentrated arc energy
• Very low dilution rate
• High-quality wear-resistant layer

Advantages:

• Excellent hardness control
• Strong metallurgical bonding
• Ideal for high-performance wear parts

Key Stages of Weld Overlay Manufacturing

1. Base Plate Preparation

• Cleaning oil, rust, and impurities
• Surface grinding or shot blasting
• Ensuring proper welding surface condition

2. Preheating (if required)

• Reduces thermal stress
• Prevents cracking in high-carbon or thick plates
• Typically used for thick base materials

3. Overlay Welding

• Deposition of wear-resistant alloy layer
• Controlled heat input
• Multi-layer welding for thick overlays

4. Cooling Process

• Controlled cooling to avoid cracking
• Prevents residual stress accumulation
• Ensures stable microstructure formation

5. Post-Weld Treatment

• Surface leveling or grinding
• Inspection of hardness and bonding quality
• Dimensional correction if required

Formation of Wear-Resistant Layer

During welding, alloying elements such as chromium and carbon form hard carbide structures:

• Cr₇C₃
• Cr₂₃C₆

These carbide phases are evenly distributed in the weld matrix, creating a highly wear-resistant surface.

Key Process Control Factors

Factor	Influence
Heat Input	Controls hardness and dilution
Welding Speed	Affects layer uniformity
Cooling Rate	Determines crack resistance
Alloy Composition	Defines wear resistance level
Layer Thickness	Impacts service life

Advantages of Weld Overlay Plate

• Extremely high surface hardness (55–65 HRC)
• Strong metallurgical bonding to base plate
• Customizable wear resistance performance
• Long service life in abrasive environments
• Suitable for large-scale industrial production

Typical Applications

Weld overlay plates are widely used in:

• Mining equipment liners
• Cement plant chutes and hoppers
• Coal handling systems
• Power plant ash systems
• Steel mill wear parts
• Crusher and conveyor systems
• Bulk material transfer equipment