Development of Wear-Resistant Surfacing Material for Impact Abrasive Wear Conditions

Literature Overview

Published in Surface Technology in 2004 by Liu Zhengjun and colleagues from Shenyang University of Technology, this paper reports on the development of a wear-resistant surfacing electrode for components subjected to impact abrasive wear. The research addresses a specific and challenging wear condition where both abrasive particles and impact loading contribute to material removal. The resulting Fe-Mn-Cr-Mo-V alloy system electrode was validated through laboratory testing and field application.

Core Technical Findings

The developed surfacing electrode is based on an Fe-Mn-Cr-Mo-V alloy system. The key performance characteristics include:

The work-hardening mechanism is central to the wear resistance of this material. Under impact abrasive conditions, the martensitic or austenitic structure of the surfacing layer undergoes plastic deformation, leading to dislocation multiplication, strain hardening, and in some cases, transformation-induced plasticity (TRIP). This in-situ hardening allows the material to adapt to increasing wear severity, providing a self-reinforcing protection mechanism.

Process and Metallurgical Analysis

The Fe-Mn-Cr-Mo-V alloy system is selected for its combination of ductility, work-hardening capacity, and wear resistance. Manganese promotes the formation of retained austenite, which provides a reservoir for TRIP hardening. Chromium enhances corrosion resistance and contributes to carbide formation. Molybdenum improves hardenability and high-temperature strength. Vanadium forms fine carbides that refine the grain structure and provide additional hardening.

The impact abrasive wear mechanism involves a combination of sliding abrasion and impact loading. During impact, the material undergoes plastic deformation, leading to work hardening. During sliding, the hardened surface resists further material removal. This synergistic mechanism results in superior wear performance compared to materials that rely solely on static hardness.

The work-hardening rate is a critical parameter for impact abrasive applications. Materials with a high work-hardening rate can achieve higher hardness under service conditions than their as-deposited hardness. This means that the material becomes harder as it is worn, providing a self-adjusting protection mechanism. This is in contrast to materials with low work-hardening rates, which may wear rapidly and fail to develop adequate surface hardness.

The chipping-type impact wear mechanism involves the formation of microcracks at the surface, which propagate under repeated impact loading. The Fe-Mn-Cr-Mo-V alloy system resists this mechanism through its combination of toughness and work-hardening capacity. The retained austenite phase absorbs impact energy through transformation, while the work-hardened martensite provides resistance to crack propagation.

Engineering Practice Integration

This surfacing electrode is applicable to a range of components in the pipe and fitting industry that experience impact abrasive wear:

1. Crusher hammers and jaws: These components are subjected to repeated impact loading from falling ore, combined with abrasive wear from hard particles.
2. Excavator buckets and teeth: Similar to crusher components, these experience impact and abrasion during material handling.
3. Pipe and fitting repair: Components in slurry transport systems may experience impact from debris or flow-induced vibration, combined with abrasive wear.
4. Valve components: Valve seats and stems in aggressive service conditions may experience impact from debris, combined with abrasive wear.

The good welding processability of the electrode makes it suitable for field application, where access and equipment limitations are common. The low spatter and easy slag removal reduce post-weld cleanup time, which is important for maintaining productivity in repair operations.

When applying this electrode, the following process considerations are important:

1. Preheat temperature: 100 to 150°C to reduce hydrogen-induced cracking risk.
2. Interpass temperature: Maintain below 250°C to ensure adequate work-hardening capacity.
3. Deposit thickness: 3 to 5 mm per pass to balance dilution control with mechanical performance.
4. Post-weld inspection: Visual examination and hardness measurement to verify adequate work-hardening potential.

Key Questions and Reflections

A critical consideration is the relationship between the as-deposited hardness and the service hardness after work hardening. Engineers should understand that the as-deposited hardness may not reflect the actual hardness achieved during service. This means that hardness specifications for impact abrasive applications should be based on post-service hardness, not as-deposited hardness.

Another question is the effect of base metal dilution on the work-hardening capacity. If the base metal has a low work-hardening rate, dilution could reduce the overall work-hardening capacity of the surfacing layer. This is particularly relevant for repairs on carbon steel components, where the base metal has limited work-hardening potential.

The field application results reported in this study provide valuable validation, but the specific service conditions are not detailed. Engineers should evaluate whether the wear conditions in their application are similar to those tested in the study. Impact abrasive wear can vary significantly depending on particle size, impact velocity, and loading frequency.

Study Insights and Implications

This research demonstrates that the Fe-Mn-Cr-Mo-V alloy system is an effective choice for surfacing applications involving impact abrasive wear. The high work-hardening rate provides a self-reinforcing protection mechanism that adapts to increasing wear severity. This is a significant advantage over materials that rely solely on static hardness.

The findings also highlight the importance of understanding the wear mechanism when selecting surfacing materials. Impact abrasive wear requires a different approach than pure sliding abrasion. Materials with high static hardness but low work-hardening capacity may perform poorly under impact loading, while materials with moderate static hardness but high work-hardening capacity may perform excellently.

For the pipe and fitting industry, this work supports the development of specialized surfacing consumables for specific wear conditions. Rather than using a one-size-fits-all approach, engineers should select surfacing materials based on a detailed understanding of the wear mechanism and the properties required to resist it.