Submerged Arc Overlay Welding of Cemented Carbide Steel Bimetallic Composites

Literature Overview

This 2008 paper by Cai Mei and colleagues from Xi'an University of Architecture and Technology introduces a novel manufacturing process for cemented carbide-steel bimetallic composite materials using submerged arc automatic overlay welding. The work bridges the gap between traditional powder metallurgy-based composite fabrication and arc welding techniques, offering a scalable and cost-effective alternative for producing wear-resistant surfaces.

Process Description and Technical Parameters

The submerged arc overlay welding (SAOW) process described in this paper involves placing cemented carbide particles or inserts on the steel substrate surface and then performing automatic submerged arc welding to fuse the carbide into the steel matrix. The key process parameters and material specifications are summarized below:

The use of submerged arc welding for this application is particularly advantageous because:

• The flux provides excellent shielding, preventing carbide oxidation during the welding process
• High deposition rates enable thick composite layers to be built efficiently
• The process is amenable to automation, ensuring consistent quality
• The molten pool temperature is sufficient to achieve metallurgical bonding between the carbide and steel

Microstructural Analysis and Interface Bonding

The authors employed SEM, EDS, and XRD to characterize the composite material. The key findings regarding the interface are:

1. Metallurgical bonding exists between the cemented carbide and the steel matrix, as confirmed by the absence of cracks, voids, or delamination at the interface.
2. Uniform hardness transition is observed from the hard carbide particles to the softer steel matrix, indicating good compatibility and reduced risk of interfacial cracking during service.
3. The carbide particles are embedded within a martensitic or bainitic matrix, providing a composite effect where the hard phase resists abrasion while the tough matrix absorbs impact energy.

The metallurgical bonding is achieved because the welding temperature exceeds the melting point of the steel substrate and the cobalt binder in the cemented carbide. This creates a diffusion zone at the interface where iron and cobalt atoms intermix, forming a continuous metallic bond.

Wear Performance Analysis

The three-body abrasive wear test is particularly relevant to engineering applications involving:

• Slurry transport piping
• Pump impellers and casings
• Mining equipment linings
• Conveyor systems handling abrasive materials

The 3.7× improvement in wear resistance over normalized 45 steel represents a substantial performance gain. However, it is important to note that:

• The wear test was conducted at room temperature, which may not represent all service conditions
• Three-body abrasive wear involves harder particles trapped between two surfaces, which is more severe than two-body abrasion
• The actual service life improvement depends on the specific operating environment, load, and sliding velocity

Engineering Practice Integration

For piping and equipment engineers, this composite manufacturing approach offers several practical advantages:

• In-situ repair capability: Wear-damaged pipe surfaces can be restored by applying the carbide-steel composite overlay, extending component life significantly.
• Design flexibility: The composite can be applied selectively to high-wear zones rather than making the entire component from expensive wear-resistant material.
• Process compatibility: Submerged arc welding is already widely used in pipe manufacturing (LSAW, UOE processes), so the equipment and expertise are readily available.

A critical consideration is the residual stress introduced by the welding process. The large thermal gradient between the thin composite layer and the thick steel substrate can generate significant tensile residual stresses at the interface, potentially leading to spalling during abrasive service. Post-weld stress relief or controlled cooling rates may be necessary for demanding applications.

Study Insights

This paper demonstrates that conventional welding processes can be adapted to produce advanced composite materials without requiring specialized powder metallurgy or thermal spray equipment. The submerged arc process, with its high deposition rate and excellent shielding, is ideally suited for thick overlay applications. The key to success lies in the particle size selection, flux composition, and welding parameter optimization to ensure complete melting of the carbide binder without excessive carbide dissolution. For engineers evaluating repair strategies for abrasive-service piping, this approach warrants serious consideration as a cost-effective alternative to full component replacement.