Research on Cladding Electrodes Combining Crack Resistance and Wear Resistance

Overview and Research Background

This study, conducted by Yang Shanglai, Zou Zengda, Qu Ganyao, and Zou Yong from Shandong University of Technology and Lunan Fertilizer Plant in 2000, addresses a fundamental challenge in hardfacing metallurgy: achieving simultaneous crack resistance and wear resistance in cladding electrodes. The research was supported by the Shandong Provincial Natural Science Foundation (Grant No. 961144104). The industrial motivation stems from the severe abrasive and erosive conditions encountered in fertilizer plant equipment, where components such as pumps, valves, and mixers are subjected to continuous mechanical wear and thermal cycling. Conventional hardfacing alloys often exhibit a trade-off between toughness and hardness, making it difficult to deploy them in applications where both properties are simultaneously required. The researchers approached this problem by systematically investigating electrode composition, microstructure, and performance characteristics under controlled laboratory and field conditions.

Core Technical Approach

The fundamental strategy employed in this research was to develop a multi-layer cladding electrode system that decouples the crack resistance requirement from the wear resistance requirement through layered design. The base layer, deposited directly onto the substrate, was formulated with enhanced toughness to accommodate thermal stresses and prevent interfacial cracking during deposition and subsequent service. The intermediate layer served as a transition zone, gradually modifying the microstructure from the base layer composition toward the hardfacing composition. The cover layer, designed with high hardness constituents such as carbides and martensite, provided the primary wear resistance. This multi-layer approach reflects a well-established principle in hardfacing metallurgy that the properties of each layer can be independently optimized while maintaining metallurgical compatibility across the interface.

The following table summarizes the key design parameters and target properties for each layer:

Layer	Primary Function	Key Alloying Elements	Target Hardness (HV)	Target Toughness
Base Layer	Crack resistance, substrate bonding	Ni, Mo, Mn	200-300	High
Intermediate Layer	Transition, stress relief	Cr, Mo, Ni	300-450	Moderate
Cover Layer	Wear resistance	Cr, C, W, V	600-800	Low

The researchers conducted extensive metallographic analysis to characterize the microstructure of each layer, including the distribution and morphology of carbides, the type of matrix phase (ferrite, austenite, or martensite), and the nature of interfacial bonding. The crack resistance was evaluated through bend tests and thermal cycling tests, while wear resistance was assessed using pin-on-disk abrasion tests against standardized counterfaces.

Process Parameters and Welding Considerations

The welding process employed was manual metal arc welding (SMAW) using the developed multi-layer electrodes. The following process parameters were identified as critical for achieving the desired performance:

Parameter	Recommended Range	Rationale
Preheat Temperature	150-250°C	Reduce thermal gradient, prevent base metal cracking
Interpass Temperature	150-250°C	Maintain heat input consistency
Arc Length	2-3 mm	Ensure stable arc and proper penetration
Travel Speed	Moderate to Slow	Allow adequate solidification and phase transformation
Layer Thickness	2-4 mm per pass	Balance dilution and property gradient
Post-Weld Heat Treatment	550-650°C for 2 hours	Relieve residual stresses, temper martensite

The preheat and interpass temperature control is particularly critical for the base layer, where the thermal gradient between the hot weld metal and the relatively cold base metal can induce significant residual stresses. Without adequate preheat, microcracking at the fusion boundary is a common failure mode, especially when the base metal is a low-carbon or low-alloy steel with limited hydrogen embrittlement resistance. The post-weld heat treatment serves a dual purpose: relieving residual stresses that could lead to delayed cracking, and tempering the hard martensitic phase in the cover layer to achieve a more stable and ductile microstructure without significantly sacrificing hardness.

Key Findings and Engineering Implications

The research demonstrated that the multi-layer electrode system achieved a hardness of approximately 650 HV in the cover layer while maintaining sufficient toughness to survive thermal cycling without catastrophic cracking. The base layer exhibited a fully austenitic or austenitic-ferrite microstructure with excellent ductility, effectively absorbing thermal strains during welding and service. The intermediate layer showed a mixed microstructure with fine carbides dispersed in a martensitic matrix, providing a smooth transition in both composition and mechanical properties.

From an engineering practice perspective, this research highlights several important principles that remain relevant today. First, the layered design philosophy allows engineers to independently optimize each layer for its specific function, which is far more effective than attempting to achieve all properties in a single homogeneous layer. Second, the importance of process parameter control, particularly preheat and interpass temperature, cannot be overstated in hardfacing applications involving thick sections or high-carbon substrates. Third, the post-weld heat treatment step, while often neglected in field applications, is essential for achieving the full performance potential of the cladding system.

The study also underscores the value of combining academic research with industrial collaboration. The involvement of Lunan Fertilizer Plant provided real-world service conditions and failure data that guided the research direction, while the academic team contributed systematic experimental methodology and materials characterization capabilities. This model of industry-university collaboration remains a best practice for advancing hardfacing technology in industrial settings.

Reflections and Practical Guidance

After reviewing this research, several practical lessons emerge for engineers working with hardfacing applications. The concept of layered design with functionally graded properties should be the default approach whenever a component is subjected to combined wear and cracking mechanisms. Engineers should not assume that a single hardfacing alloy can satisfy all performance requirements; instead, they should design a multi-layer system with carefully selected base, transition, and cover layers. Furthermore, the research reinforces the importance of comprehensive process qualification, including metallographic examination of each layer, hardness profiling across the full cladding thickness, and service simulation testing under realistic thermal and mechanical loading conditions.