Development of Iron-Based High-Temperature Wear-Resistant Alloy Overlay Welding Electrodes

Literature Overview

This 1996 study by Xu Guojian and Gu Yuxi from Shenyang University of Technology, in collaboration with Zhou Ye from Shenyang High Voltage Switchgear Co., Ltd., represents an early and pioneering effort in developing iron-based overlay welding electrodes specifically designed for high-temperature wear applications. Published in the Journal of Shenyang University of Technology, this work bridges academic research and industrial application, targeting the specific needs of high-voltage switchgear components that experience arc erosion and thermal cycling.

Core Technical Content

The application context is critical to understanding the research motivation. High-voltage switchgear contacts and arc chutes experience extreme conditions: temperatures reaching 1500–3000°C during arc events, rapid thermal cycling, electrical erosion, and mechanical wear from contact separation. Conventional hardfacing alloys either soften excessively above 400°C or become too brittle for impact loading. The researchers sought to develop an iron-based system that could maintain functional hardness above 600°C while retaining sufficient toughness for thermal shock resistance.

Alloy Design Approach

The alloy development followed a systematic approach based on thermodynamic calculations and experimental validation:

1. Base system: Fe-Cr-Mo-C with 10–14% Cr, 3–5% Mo, and 0.8–1.2% C as the primary hardening platform
2. High-temperature stabilizers: 3–5% W and 2–3% V to retard carbide coarsening and matrix softening
3. Thermal shock resistance: 1–2% Ni to improve austenite stability and reduce thermal expansion mismatch
4. Oxidation resistance: 0.5–1.5% Al to promote protective oxide film formation at elevated temperatures

High-Temperature Performance

The key performance metric is hardness retention at elevated temperatures. The researchers conducted hardness testing at 25°C, 400°C, 600°C, 800°C, and 1000°C after 1-hour isothermal exposure. Design 4 emerged as the optimal balance:

• 25°C: HRC 60
• 400°C: HRC 58 (97% retention)
• 600°C: HRC 54 (90% retention)
• 800°C: HRC 46 (77% retention)
• 1000°C: HRC 35 (58% retention)

This performance significantly exceeds that of conventional Cr-Mo hardfacing alloys, which typically retain only 50–60% of their hardness at 600°C.

Microstructural Evolution

Metallographic analysis revealed that the high-temperature stability is achieved through a multi-scale carbide architecture:

• Coarse primary M7C3 carbides (2–5 μm) in the martensitic matrix provide the base wear resistance
• Medium M23C6 carbides (0.5–2 μm) at grain boundaries provide thermal stability
• Fine WC and VC particles (50–200 nm) dispersed throughout the matrix resist coarsening even at 800°C
• Retained austenite (5–10% volume fraction) stabilized by Ni provides thermal shock resistance and crack arrest capability

Weldability Assessment

The electrodes were evaluated for weldability using standard coupon tests:

• Cracking sensitivity: No hot cracking observed with interpass temperature below 200°C
• Hydrogen cracking: Susceptible above 150°C interpass temperature; requires preheating to 100–150°C and post-weld heat treatment
• Dilution: 15–20% base metal dilution in the first pass; compensated by enriched first-pass composition
• Bond strength: 350–400 MPa shear strength to 45 steel substrate

Engineering Application and Industrial Validation

The collaboration with Shenyang High Voltage Switchgear Co., Ltd. provided critical industrial validation. The developed electrodes were applied to arc chute components and contact plates in 126 kV GIS (Gas Insulated Switchgear) equipment. Field trials demonstrated:

• 3–5× improvement in contact plate service life compared to uncoated components
• Reduced arc erosion depth from 2.5 mm to 0.6 mm per 10,000 operations
• Acceptable performance through 50,000 switching cycles without coating spalling or delamination

Study Reflections

This 1996 research was remarkably forward-looking in its approach to high-temperature hardfacing alloy design. The multi-element strategy combining Cr, Mo, W, V, Ni, and Al was validated by later research and commercial product development. The concept of retained austenite as a thermal shock resistance mechanism, while known in principle, was not widely applied in hardfacing alloy design at that time. The industrial validation through actual switchgear application provides strong evidence that laboratory-optimized compositions can be successfully transferred to production applications. For modern engineers working on hardfacing for electrical equipment, nuclear components, or aerospace hot sections, this work provides a proven design philosophy that remains applicable with updated analytical tools and manufacturing capabilities.