Research Progress on Wear-Resistant Overlay Alloy Materials

Literature Overview

The review paper by Meng Yuanyuan, Ren Ruichen, Zhang Qianwei, and Qin Haifeng, published in Materials Protection (2016), provides a comprehensive overview of research progress on wear-resistant overlay alloy materials. The authors are affiliated with the School of Mining Technology and the School of Mining Engineering at Liaoning Technical University, with Qin Haifeng representing Fushun Petrochemical Company Acrylic Fiber Plant. This work synthesizes findings from multiple research groups and industrial applications, offering a valuable reference for engineers selecting overlay materials for wear protection applications.

Classification and Properties of Wear-Resistant Overlay Alloys

Wear-resistant overlay alloys can be broadly classified into four categories based on their matrix composition and hard phase morphology. Each category exhibits distinct wear mechanisms and is suited for specific service environments.

Category	Matrix Composition	Hard Phase	Typical Hardness (HV)	Wear Mechanism Resistance
High-carbon martensitic	Fe-2.0–3.5C-10–18Cr	Cementite, Cr7C3	800–1100	Abrasive, adhesive
Carbide-forming	Fe-2.0–3.5C-10–18Cr-5–10W	WC, Cr7C3, Fe3C	1000–1400	Abrasive, erosive
Boride-forming	Fe-2.0–3.5C-10–18Cr-2–5B	CrB, Fe2B, B4C	900–1300	Abrasive, high-temperature
Composite reinforced	Fe-Cr-C with WC, CrC, TiC particles	Dispersed particles	1100–1500	Abrasive, impact-abrasive

The high-carbon martensitic overlay alloys are the most widely used due to their excellent combination of hardness, toughness, and weldability. The carbon content is critical in determining the microstructure; below 1.5 percent carbon, the matrix consists primarily of tempered martensite with limited cementite precipitation, while above 3.5 percent carbon, excessive brittle cementite networks form that compromise toughness. The optimal carbon range of 2.0 to 3.5 percent provides a balanced microstructure with high hardness and adequate ductility.

The addition of alloying elements significantly modifies the properties of overlay alloys. Chromium improves both hardness and corrosion resistance by forming stable carbides and promoting the formation of protective oxide scales. Tungsten increases hardness through solid solution strengthening and the formation of hard WC and W2C carbides. Molybdenum enhances hot hardness and resistance to thermal fatigue. Vanadium and niobium form fine, stable carbides that provide excellent resistance to fine-particle abrasive wear.

Wear Mechanisms and Material Selection

Understanding the dominant wear mechanism is essential for selecting the appropriate overlay alloy. Abrasive wear, which accounts for the majority of wear failures in industrial applications, can be further classified into two-body abrasion (where hard particles are embedded in a softer counterface) and three-body abrasion (where loose particles are trapped between contacting surfaces). The overlay material must be sufficiently hard to resist material removal while maintaining adequate toughness to prevent catastrophic fracture.

Wear Condition	Recommended Overlay	Key Alloying Elements	Typical Application
Hard particle abrasion	High-carbon Cr-W alloy	Cr 14–18%, W 5–10%	Mining equipment, crushers
Soft particle abrasion	Medium-carbon Cr alloy	Cr 10–14%, C 2.0–2.5%	Conveyor systems, hoppers
High-temperature abrasion	Cr-Mo-W alloy	Cr 12–16%, Mo 2–5%, W 3–6%	Kilns, furnace linings
Impact-abrasive	Low-carbon Cr-Ni alloy	Cr 8–12%, Ni 3–6%, C 1.5–2.0%	Excavator buckets, screens
Corrosive-abrasive	High-Cr-Ni alloy	Cr 20–30%, Ni 5–10%	Chemical processing equipment

The review highlights that the relationship between overlay hardness and wear life is not linear. For abrasive wear by hard particles, wear life increases with hardness following a power-law relationship where the exponent is approximately 1.5 to 2.0. However, for impact-abrasive conditions, there exists an optimal hardness range beyond which increased brittleness leads to premature fracture and reduced wear life.

Process-Property-Performance Relationships

The overlay process parameters significantly influence the final properties of the deposited layer. Submerged arc welding (SAW) produces the thickest, most uniform layers with the lowest dilution ratios, making it suitable for heavy-duty applications. Gas metal arc welding (GMAW) offers excellent productivity for medium-thickness deposits. Gas tungsten arc welding (GTAW) provides the finest microstructure and lowest dilution, suitable for precision overlay applications. Thermal spray processes including flame spraying and plasma spraying can achieve very high hardness levels but with lower bond strength compared to fusion welding methods.

Process	Typical Thickness	Dilution Ratio	Hardness (HV)	Productivity	Cost Index
SAW (single-wire)	3–8 mm	15–25%	900–1100	High	1.0
SAW (multi-wire)	5–15 mm	10–20%	850–1050	Very High	1.2
GMAW	2–5 mm	20–35%	800–1000	High	0.8
GTAW	0.5–2 mm	5–15%	950–1200	Low	2.5
PTA	0.5–3 mm	5–15%	1000–1400	Medium	3.0
Laser cladding	0.2–1.5 mm	2–10%	1100–1500	Low	4.0
Flame spraying	0.5–3 mm	0% (non-fusion)	800–1100	High	1.5

The dilution ratio is a critical parameter that directly affects the final composition and properties of the overlay layer. For applications requiring specific microstructural features such as carbide morphology and distribution, dilution must be carefully controlled. The multi-wire SAW process offers the advantage of independent control over wire feed rates, allowing real-time adjustment of the dilution ratio during welding.

Engineering Applications and Case Studies

The review documents several successful industrial applications of wear-resistant overlay alloys. In mining operations, overlay of crusher jaws and cone liners with high-carbon Cr-W alloys extended service life by 3 to 5 times compared to unhardened surfaces. In cement manufacturing, kiln wear plates overlaid with Cr-Mo-W alloys achieved service intervals of 18 to 24 months compared to 6 to 8 months for standard plates. In power generation, boiler furnace water walls protected with impact-abrasive overlay alloys reduced unplanned shutdowns by 60 percent.

The economic analysis presented in the review demonstrates that overlay protection typically pays for itself within 6 to 12 months of operation, with subsequent years representing pure savings. The total cost of ownership approach, which includes material costs, labor, downtime, and maintenance, consistently favors overlay protection over periodic replacement of worn components.

Study Insights and Reflections

This comprehensive review serves as an essential reference for engineers involved in wear protection design and implementation. The systematic classification of overlay alloys by matrix composition and hard phase morphology provides a clear framework for material selection. The process-property-performance relationships documented here enable engineers to make informed decisions about the most suitable deposition method for specific applications. The economic analysis reinforces the business case for investment in overlay protection technology, demonstrating that proactive wear management through surface engineering delivers substantial returns in terms of reduced downtime, extended equipment life, and improved operational efficiency. Future research directions should focus on developing multilayer overlay designs that combine different wear mechanisms resistance in a single component, and on integrating computational tools for predicting overlay performance under complex service conditions.