Effect of Rare Earth Elements on Austenitic Overlay Welding Electrode Metal Microstructure and Properties

Literature Overview

Hong Yongchang, Feng Anhua, Qing Hua, and Huang Ming (1998, Welding Technology, Vol. 27, No. 4, pp. 5–7) systematically investigated the influence of rare earth elements (Y, Ce, La) added to austenitic-based overlay welding electrodes on the as-welded microstructure and mechanical properties of the overlay layer. The research was conducted in collaboration with Masteel Jiangdong Welding Electrode Factory, reflecting strong industry-academia integration.

Core Technical Findings

The introduction of rare earth elements into austenitic overlay welding electrodes produces measurable improvements in as-welded microstructure quality, as-welded hardness, age-hardened hardness, wear resistance, and thermal fatigue resistance. These improvements are attributed to the well-documented effects of rare earth elements on solidification behavior, grain refinement, and inclusion modification in steel systems.

Rare Earth Element Effects

Metallurgical Mechanisms

Rare earth elements act as:

1. Deoxidizers and desulfurizers: Reducing harmful inclusions that serve as crack initiation sites.
2. Grain refiners: Modifying the solidification front morphology to promote equiaxed grain formation.
3. Interfacial modifiers: Altering the morphology of inclusions from elongated to spherical, reducing stress concentration.
4. Precipitation promoters: Influencing the nucleation and growth of strengthening phases during aging.

Engineering Application Context

Austenitic overlay welding electrodes are commonly used in applications requiring simultaneous resistance to high-temperature oxidation and abrasive wear, such as:

• Coal handling equipment (chutes, hoppers, conveyor rollers)
• Cement kiln components
• Power plant boiler tubes and burners
• Mining and quarrying equipment

Implementation Considerations

1. Rare earth addition level: Typical addition levels range from 0.01% to 0.10% by mass; excessive addition can lead to segregation and property degradation.
2. Electrode coating design: Rare earth compounds (typically rare earth silicates or carbonates) are incorporated into the electrode flux coating for controlled release during welding.
3. Storage and handling: Rare earth-containing electrodes require careful moisture control due to the hygroscopic nature of many rare earth compounds.
4. Welding parameter sensitivity: Rare earth additions may slightly alter the arc stability and spatter characteristics, requiring minor parameter adjustments.

Study Insights and Reflections

This 1998 study predates the widespread commercial adoption of rare earth modifications in welding consumables, yet its findings align with subsequent decades of research confirming the beneficial effects of rare earth elements in steel welding systems. The comprehensive evaluation of both as-welded and aged properties is particularly noteworthy, as many studies focus only on the as-deposited condition. For austenitic overlay applications in high-temperature environments, the thermal fatigue resistance improvement is arguably the most significant benefit, as thermal cycling is often the primary degradation mechanism in service. The industry-academia collaboration model demonstrated in this work—conducted jointly with an electrode manufacturer—provides an excellent example of how fundamental research can be directly translated into product development. The progressive understanding of rare earth effects in welding has since led to their inclusion in many modern welding consumable specifications, particularly for critical applications in power generation and heavy industry.