Special Wear-Resistant Surfacing Electrodes

Literature Overview

This technical article by Sun Weijun from Beijing Tiangongyu Industry and Trade Company, published in New Technology and New Process (2002, No. 5, p. 26), introduces special wear-resistant surfacing electrodes, with particular focus on the D60 electrode. The paper addresses the selection and application of surfacing electrodes for hardfacing applications in industrial environments where components are subjected to severe abrasive and erosive wear.

Electrode Classification and Composition

Wear-resistant surfacing electrodes are classified according to the hard phase they deposit, which determines their wear resistance mechanism and application range. The following table summarizes the major categories:

Electrode Type	Hard Phase	Typical Composition	Application
Cast iron type	Cementite (Fe₃C)	High carbon, manganese	Abrasive wear, moderate impact
Alloy steel type	Carbides (Cr₇C₃, WC, Mo₂C)	High Cr, W, Mo	Severe abrasive wear
Stellite type	Cr-Cr₇C₃	Co-Cr-W-C	High-temperature wear, corrosion
Overlay type	Multi-layer	Fe-Cr-C or Ni-Cr-C	Corrosion-wear combined

The D60 electrode, discussed in this paper, belongs to the alloy steel type with a high chromium and tungsten composition. It deposits a hard layer containing primary carbides that provide excellent resistance to abrasive wear.

Key Performance Characteristics of D60 Electrode

Hardness: 58-64 HRC as-deposited, 60-66 HRC after tempering
Carbide content: High volume fraction of hard carbides (Cr₇C₃, W₂C)
Weldability: Requires preheating and controlled heat input to prevent cracking
Typical application: Coal handling equipment, mining machinery, cement mills, and other components subject to severe sliding or abrasive wear

Welding Process Requirements

Hardfacing electrodes, particularly those with high carbon and alloy content, are prone to cracking due to the high hardness and brittleness of the deposited layer. The following process controls are essential:

Preheating: Preheat the base material to 200-400°C to reduce thermal gradients and hydrogen-induced cracking
Interpass temperature: Maintain at 200-300°C to minimize thermal stress between passes
Heat input control: Use moderate current and travel speed to avoid excessive dilution and cracking
Post-weld heat treatment: Tempering at 600-650°C for 1-2 hours per 25 mm of buildup thickness to reduce residual stress and improve toughness
Layer thickness: Apply in multiple thin layers (2-4 mm each) to avoid excessive internal stress

Application Cases

The D60 electrode and similar hardfacing consumables have been successfully applied to:

Screw conveyor flights: In cement and coal handling systems, where abrasive material causes rapid wear of the flights
Crusher hammers and jaws: In mining and aggregate processing, where impact and abrasion are combined
Pump impellers and vanes: In slurry handling applications, where erosion and cavitation are present
Excavator bucket teeth: In earthmoving operations, where cutting edges are subject to severe abrasive wear

Defect Analysis and Countermeasures

Defect	Cause	Countermeasure
Cracking	High carbon, high hardness, thermal stress	Preheat, controlled interpass temperature, post-weld tempering
Porosity	Flux moisture, surface contamination	Dry flux, clean surface, proper electrode storage
Incomplete fusion	Insufficient heat input, poor technique	Increase current, improve torch angle, clean base metal
Spalling	Excessive hardness, poor base metal preparation	Reduce layer thickness, ensure good fusion, temper after welding

Study Insights and Implications

This paper, while brief, highlights the importance of electrode selection in hardfacing applications. The D60 electrode represents a well-established solution for abrasive wear protection, but its successful application requires careful attention to welding process parameters and post-weld treatment. The key insight is that hardfacing is not merely about depositing a hard layer; it is about achieving a balance between hardness (for wear resistance) and toughness (to prevent spalling and cracking).

For modern engineers, the principles described in this paper remain relevant, but the field has evolved significantly with the development of advanced hardfacing alloys, flux-cored wire consumables, and automated hardfacing systems. The fundamental challenge—managing the trade-off between hardness and crack resistance—remains central to hardfacing technology.