Development of Iron-Based High-Temperature Wear-Resistant Hardfacing Electrode with Cr-Mo-B System

Literature Overview

Published in 1996 by Xu Guojian and colleagues from Shenyang University of Technology in collaboration with Shenyang High Voltage Switchgear Co., Ltd., this paper describes the development of an iron-based Cr-Mo-B alloy hardfacing electrode designed for high-temperature wear applications. The electrode produces a weld deposit with martensitic matrix containing boride and carbide eutectic phases, achieving both high room-temperature wear resistance and excellent red hardness (hot hardness). Field trials on brick-making machine mixer blades demonstrated more than a fivefold improvement in service life compared to quenched 45 steel.

Alloy System and Microstructural Design

The Cr-Mo-B iron-based system was selected to leverage the formation of multiple hard phases at high temperatures. The microstructure of the deposited layer consists of:

The key design philosophy is to create a composite microstructure where multiple hard phases with different melting points and thermal stabilities provide wear resistance across a wide temperature range.

Performance Characterization

The quantitative performance data reported in this study is particularly valuable for engineering specification:

The hardness retention at 700°C (HV 306.4) is particularly remarkable for an iron-based system. Most conventional hardfacing alloys lose significant hardness above 500°C due to carbide coarsening, martensite decomposition, and phase transformations. The presence of borides (Fe2B, CrB) and stable carbides (Mo2C, Cr7C7) provides resistance to these degradation mechanisms.

Practical Application: Brick-Making Machine Mixer Blades

The field trial on brick-making machine double-shaft mixer blades provides compelling evidence of the electrode's practical value. These blades operate under:

• Continuous abrasive contact with wet clay and sand mixtures
• Impact loading from material being mixed
• Temperatures elevated by friction and ambient conditions
• Constant exposure to abrasive mineral particles

The five-fold life improvement over quenched 45 steel demonstrates that the Cr-Mo-B hardfacing system effectively addresses the combined damage mechanisms in this application.

Engineering Design Principles

This study illustrates several important principles for high-temperature hardfacing design:

1. Multi-phase hardening: Combining borides and carbides provides complementary thermal stability
2. Martensitic matrix: Retains strength at elevated temperatures while providing toughness
3. Boron incorporation: Lowers boride formation temperature and improves phase stability
4. Molybdenum addition: Forms extremely stable carbides (Mo2C) with high melting point
5. Eutectic microstructure: Maximizes the volume fraction of hard phases through controlled solidification

Summary

This 1996 paper represents a classic example of practical hardfacing material development driven by specific industrial needs. The Cr-Mo-B iron-based system achieved remarkable performance improvements in a demanding application, with quantifiable results that directly support economic justification for adoption. The five-fold life extension on mixer blades, combined with hardness retention at 700°C, demonstrates the effectiveness of multi-phase design philosophy in high-temperature wear applications. Engineers specifying hardfacing for elevated-temperature abrasive service should consider boride-containing iron-based systems as a viable alternative to more expensive nickel or cobalt-based alloys.