Performance of a New High-Temperature Oxidation Resistant Cladding Electrode

Literature Overview

This study, published in China Surface Engineering in 2008 by Li Xiaofeng, Chen Bingquan, Lü Kuirong, Liu Yushuang, and Zhang Lian from Wuhan University of Technology, Wuhan Iron Anchor Welding Materials Co., Ltd., and Wuhan Institute of Materials Protection, investigates the development and performance of a new high-temperature oxidation resistant cladding electrode. The research addresses the challenge of protecting components exposed to high-temperature oxidation environments, such as furnace parts, heat exchangers, and power generation equipment, by developing a cladding electrode with superior oxidation resistance at elevated temperatures.

Core Technical Content

The study focuses on the development of a shielded metal arc welding (SMAW) electrode with a cladding layer composition optimized for high-temperature oxidation resistance. The electrode is designed to be deposited on carbon steel or low-alloy steel substrates to create a protective cladding layer that resists oxidation at temperatures up to 1000 °C.

Electrode Composition

The cladding layer composition of the developed electrode is as follows:

The high chromium content (22–26 wt%) provides the primary oxidation resistance through the formation of a protective chromium oxide scale. The addition of aluminum (2.0–4.0 wt%) enhances the oxidation resistance through the formation of a stable aluminum oxide layer, while molybdenum and nickel improve the high-temperature strength and thermal fatigue resistance of the cladding layer.

Welding Parameters

The welding parameters were optimized to minimize dilution from the substrate while ensuring adequate fusion and arc stability. The use of a relatively low preheat temperature (100–150 °C) was found to be sufficient to prevent cold cracking while maintaining the high-temperature oxidation resistance of the cladding layer.

Microstructural Analysis

The cladding layer produced by the developed electrode exhibited a microstructure consisting of:

• Austenite: The primary phase, with a hardness of 200–250 HV, providing good ductility and thermal fatigue resistance.
• Ferrite: Present in small quantities (5–15%), contributing to strength and oxidation resistance.
• Chromium oxide (Cr2O3): Formed at the surface during high-temperature exposure, providing a protective barrier against further oxidation.
• Aluminum oxide (Al2O3): Formed at the surface during high-temperature exposure, enhancing the stability of the oxide scale.

The microstructure of the cladding layer near the fusion line exhibited a mixed structure of austenite and ferrite, while the surface layer showed a predominantly austenitic structure with fine chromium carbide precipitates.

Standards and Specification Considerations

The fabrication of high-temperature oxidation resistant cladding must comply with the following standards:

The welding procedure qualification must include mechanical testing (tensile, bend, impact), metallographic examination, and high-temperature oxidation testing to ensure the performance of the cladding layer.

High-Temperature Oxidation Testing

The high-temperature oxidation resistance of the cladding layer was evaluated through cyclic oxidation testing at temperatures of 800 °C, 900 °C, and 1000 °C in air. The results are summarized as follows:

The weight gain data indicates that the cladding layer exhibits significantly improved oxidation resistance compared to the bare carbon steel substrate, which exhibited weight gains of 200–500 mg/cm² under the same test conditions. The formation of a dense and adherent chromium oxide scale is the primary mechanism of oxidation protection.

Defect Analysis and Countermeasures