Wear-Resistant Parts Overlay Manufacturing and Remanufacturing Technology

Literature Overview

The paper by Liu Zhenying (2008, New Century Cement Guide, Vol. 14, No. 5, pp. 31–34), supported by a National Science and Technology Innovation Fund project, provides a systematic discussion of overlay welding technology for wear-resistant components, with a particular focus on remanufacturing applications in the cement industry. The paper addresses several key issues: the comparison between overlay-welded and cast wear-resistant parts, the advantages and disadvantages of different remanufacturing methods, the selection principles for on-line and off-line overlay, and the emerging technology of composite wear-resistant parts.

Overlay-Welded vs. Cast Wear-Resistant Parts

Characteristic	Overlay-Welded Parts	Cast Parts
Microstructure	Refine, directional solidification	Coarse, equiaxed grains
Hardness Uniformity	High (controlled by process)	Variable (casting defects)
Repairability	Easily repaired by re-overlay	Difficult (requires replacement)
Material Cost	Lower (thin wear layer on cheap substrate)	Higher (full alloy casting)
Flexibility	Can be applied to existing parts	Requires new casting
Service Life	Comparable or superior	Dependent on casting quality

The key advantage of overlay welding is the ability to create a hard, wear-resistant surface layer on a tough, low-cost base material. This graded structure combines the best properties of both materials: the base provides impact resistance and structural integrity, while the overlay provides surface hardness and abrasion resistance.

Remanufacturing Methods and Selection Principles

The paper discusses several remanufacturing approaches:

Method	Process	Applicable Scenario	Advantage	Limitation
On-line overlay	Field welding on worn component	Large, immovable parts	No disassembly required	Limited process control
Off-line overlay	Workshop welding after removal	Small to medium parts	Full process control	Requires removal and reinstallation
Composite parts	Welded overlay on new base	New production	Optimal material combination	Higher initial cost
Cast + overlay	Overlay on cast blank	High-volume production	Combines casting flexibility with overlay quality	Two-step process

The selection between on-line and off-line overlay depends on several factors: the size and weight of the component, the accessibility of the wear surface, the availability of welding equipment, and the required quality level. For large cement mill components such as grinding rollers and mill liners, on-line overlay is often the only practical option. For smaller components such as bucket elevator buckets and conveyor idlers, off-line overlay in a workshop provides better quality control.

Risk Analysis and Control Measures

The paper provides a detailed analysis of the risks associated with overlay welding of wear-resistant parts:

Risk	Cause	Consequence	Control Measure
Cracking	High carbon content, hydrogen	Component failure	Preheating, low-hydrogen flux, post-weld heat treatment
Spalling	Poor bonding, thermal mismatch	Loss of overlay layer	Proper surface preparation, bonding layer
Hardness non-uniformity	Inconsistent process parameters	Uneven wear	Process monitoring, parameter standardization
Residual stress	Thermal cycling	Distortion, premature failure	Interpass temperature control, stress relief

The risk of cracking is particularly important for high-carbon overlay layers. The use of preheating to 200–300°C and the selection of low-hydrogen welding consumables are essential. For components that will be subjected to impact loading, post-weld heat treatment (PWHT) at 600–700°C for 1–2 hours can relieve residual stresses and improve toughness.

Composite Wear-Resistant Parts: An Emerging Approach

The paper introduces the concept of composite wear-resistant parts, which combine a tough base material with a hard overlay layer through welding. This approach is particularly advantageous for parts that experience both abrasion and impact, such as bucket elevator buckets and crusher hammers. The composite structure provides:

A tough base that resists impact and fatigue failure.
A hard overlay that resists abrasive wear.
A graded interface that prevents spalling and delamination.

This approach represents a shift from the traditional "replace when worn" paradigm to a "design for life" philosophy, where the component is engineered from the outset to have a long, predictable service life.

Summary

This paper provides a valuable framework for engineers involved in the remanufacturing of wear-resistant components. The systematic analysis of methods, risks, and selection principles is directly applicable to modern industrial maintenance programs. The emphasis on risk control through process standardization and quality monitoring is particularly relevant in today's quality-conscious manufacturing environment. The concept of composite wear-resistant parts, though described over fifteen years ago, has since become a mainstream approach in many industries, validating the forward-looking perspective of this paper.