Submerged Arc Automatic Overlay Welding for Cemented Carbide-Steel Bimetallic Composite Materials

Literature Overview

This 2008 paper by Cai Mei, Wang Shuangcheng, Niu Libin, and Xu Yunhua from the Wear-Resistant Materials Research Institute of Xi'an University of Architecture and Technology presents a novel approach to manufacturing cemented carbide-steel bimetallic composite materials using submerged arc automatic overlay welding. The study introduces a new process route for creating hardfacing composites, combining the exceptional hardness and wear resistance of cemented carbide with the toughness and formability of steel, and provides comprehensive characterization of the resulting composite material through SEM, EDS, and XRD analyses, along with three-body abrasive wear testing.

Process Innovation and Methodology

Submerged Arc Automatic Overlay Welding as a Composite Manufacturing Process

The central innovation of this work is the application of submerged arc welding (SAW) in an automatic configuration to achieve metallurgical bonding between cemented carbide inserts and steel substrates. Traditional methods of joining cemented carbide to steel typically rely on brazing, soldering, or mechanical fastening, all of which involve intermediate bonding layers that may introduce weak interfaces or thermal incompatibility issues. The submerged arc overlay welding approach eliminates the need for intermediate bonding layers by achieving direct metallurgical bonding through the molten weld pool.

The process parameters for submerged arc automatic overlay welding in this application require careful control to ensure complete melting and bonding of the carbide insert while avoiding excessive melting of the steel substrate. The high thermal input of SAW is advantageous for achieving sufficient melting of the hard carbide material, but the challenge lies in balancing this thermal input to prevent excessive dilution of the carbide by the steel, which would reduce the hardness and wear resistance benefits of the composite.

Metallurgical Bonding and Interface Characterization

The SEM and EDS analyses confirmed that a clear metallurgical bond exists between the cemented carbide and the steel matrix, without the presence of intermediate intermetallic phases that might compromise interface strength. The EDS mapping revealed a uniform hardness transition across the interface, indicating good compositional gradation that helps distribute stress concentrations at the interface. The XRD analysis identified the phase composition at and near the interface, providing evidence of the metallurgical compatibility of the two materials under the welding conditions employed.

Characterization Method	Key Finding	Significance
SEM	Clear metallurgical bond at interface	No weak interface phases
EDS	Uniform hardness transition	Good stress distribution
XRD	Identified phase composition	Confirmed bonding mechanism
Hardness test	High hardness in carbide zone, gradual decrease toward steel	Optimized composite structure
Three-body abrasive wear	3.7x wear resistance vs. normalized 45 steel	Significant performance improvement

Wear Performance and Mechanism Analysis

Three-Body Abrasive Wear Testing

The three-body abrasive wear test results demonstrate that the composite material achieves a relative wear resistance of 3.7 times that of normalized 45 steel, representing a substantial improvement in wear performance. Three-body abrasive wear is a particularly relevant wear mode for many industrial applications, including mining equipment, material handling systems, and construction machinery, where hard particles are entrained between the contacting surfaces and cause material removal through ploughing and micro-cutting mechanisms.

The wear resistance improvement can be attributed to several factors:

The high hardness of the cemented carbide phase provides exceptional resistance to micro-cutting by abrasive particles.
The metallurgical bond ensures that the carbide phase remains firmly attached to the steel substrate during wear, preventing delamination or spalling.
The gradual hardness transition from the carbide to the steel provides a toughness buffer that prevents crack initiation at the interface under impact loading.

Engineering Practice Integration

For engineers considering the application of this technology in pipe fitting and equipment manufacturing, several practical considerations emerge:

The submerged arc overlay welding process is well-suited to automated production environments, offering repeatability and consistency that are essential for quality-critical applications.
The technology can be adapted for the manufacture of wear-resistant pipe fittings, particularly for applications involving abrasive slurry transport, mining slurry pipelines, and material handling chutes.
The process parameters must be optimized for each specific carbide-steel combination, as the melting behavior of different carbide compositions (WC-Co, WC-Co-Cr, TiC-based, etc.) varies significantly.
Quality control should include interface examination through cross-sectional metallography to confirm metallurgical bonding and the absence of porosity or incomplete fusion at the interface.

Critical Reflections

The study's demonstration of metallurgical bonding between cemented carbide and steel through submerged arc overlay welding is a significant process innovation. However, the paper could benefit from additional data on the mechanical properties of the composite material beyond hardness and wear resistance, including tensile strength, fracture toughness, and impact strength of the transition zone. The long-term durability of the composite under cyclic loading conditions, particularly in the presence of corrosion or elevated temperatures, would also be valuable information for engineering application decisions. Additionally, the study does not address the scalability of the process for large components or the economic comparison with traditional composite manufacturing methods.

Summary and Outlook

This research establishes submerged arc automatic overlay welding as a viable and effective process for manufacturing cemented carbide-steel bimetallic composite materials with metallurgical bonding and significantly enhanced wear resistance. The 3.7-fold improvement in abrasive wear resistance over normalized 45 steel demonstrates the practical value of this approach for wear-critical applications. For the pipe and fitting industry, this technology opens possibilities for manufacturing wear-resistant components that combine the toughness of steel with the abrasion resistance of cemented carbide, potentially extending service life in abrasive service conditions while reducing the frequency of replacement and associated downtime costs.