High-Chromium Wear-Resistant Overlay Welding Electrode Development

Literature Overview

The paper by Wang Guo-yong and Liu Xiang-yu (Hot Working Technology, 2012, Vol. 41, No. 3, pp. 162–163) reports the development of a high-chromium wear-resistant overlay welding electrode for the repair and maintenance of spiral conveyors used in charcoal manufacturing plants. While the paper is concise, it addresses a significant industrial need for cost-effective overlay welding consumables that can extend the service life of severely worn equipment components.

Technical Context

Application Background

Spiral conveyors in charcoal manufacturing plants operate under extremely harsh conditions involving:

Continuous abrasive contact with charcoal particles and ash
Elevated temperatures from hot charcoal material
Mechanical vibration and impact loading
Corrosive atmosphere containing carbon monoxide and sulfur compounds

These conditions cause rapid wear of the conveyor surface, typically requiring replacement or repair within months of operation. Overlay welding provides a practical solution by depositing a wear-resistant layer on the worn surface, restoring dimensional accuracy and extending service life.

Electrode Design Philosophy

The high-chromium electrode was designed based on the principle that chromium carbides (Cr7C3, Cr23C6) are the primary wear-resistant phases in high-chromium overlay systems. The target composition was approximately 10–15% Cr, with controlled carbon content (2.5–4.0%) to maximize carbide formation while maintaining weldability.

Electrode Specification and Performance

Chemical Composition

Element	Specification (%)	Function
C	2.5–4.0	Carbide formation, hardness
Cr	10–15	Chromium carbides, corrosion resistance
Mn	1.0–2.0	Deoxidizer, solid solution strengthening
Si	0.3–0.8	Deoxidizer, slag formation
Fe	Balance	Matrix material

Performance Characteristics

Property	Specification	Typical Value
Overlay hardness	≥ 55 HRC	58–65 HRC
Wear resistance (vs. Q235 base)	≥ 5×	6–10×
Crack resistance	Acceptable	Low cracking tendency
Slag removal	Easy	Good slag fluidity
Arc stability	Good	Stable DC arc
Position capability	Flat, horizontal	All positions with technique

Microstructure

The overlay layer exhibited a martensitic matrix with a high volume fraction of chromium carbides. The carbide morphology was predominantly rod-like and plate-like, distributed throughout the martensitic matrix. This microstructure provides excellent abrasion resistance through the combined effect of hard carbide particles and a tough martensitic binder.

Engineering Practice Considerations

Welding Procedure

For field application on spiral conveyor repair:

Surface preparation: Grind the worn surface to remove loose material, oxide, and scale. Machine to a uniform surface if dimensional restoration is required.
Preheat: 150–250°C to minimize cracking, especially on thick sections
Welding technique: Use short arcs, weave pattern for wider coverage, maintain consistent travel speed
Interpass temperature: Keep below 300°C to prevent excessive grain growth
Number of layers: 2–3 layers for 3–5 mm overlay thickness
Post-weld treatment: Stress relief at 500–600°C if cracking is a concern

Common Defects and Solutions

Defect	Cause	Solution
Cracking	High carbon content, rapid cooling	Increase preheat, reduce travel speed
Excessive porosity	Moisture in flux, inadequate shielding	Dry electrode, ensure proper storage
Poor fusion	Low heat input, surface contamination	Increase current, clean surface thoroughly
Excessive spatter	Excessive arc length	Maintain consistent short arc
Hardness variation	Inconsistent welding parameters	Standardize parameters, train welders

Study Insights

This study, while technically straightforward, addresses a practical industrial problem with a well-proven solution. The high-chromium overlay electrode system is a mature technology with decades of industrial application, and the specific formulation developed here is tailored to the unique service conditions of charcoal manufacturing. For maintenance engineers and welding supervisors, the key takeaway is that proper electrode selection, surface preparation, and welding technique are critical to achieving reliable overlay performance. The cost-effectiveness of overlay welding repair compared to component replacement makes this technology economically attractive for industrial maintenance operations, particularly where equipment downtime is costly.